<PAGE>

                                                                   Exhibit 10.19

                                 XENOPORT, INC.

                            TRAN EMPLOYMENT AGREEMENT

      This Agreement is entered into as of July 15 2004, by and between
XenoPort, Inc. (the "COMPANY"), and Pierre Tran ("EXECUTIVE").

      1. Duties and Scope of Employment.

            (a) Effective Date. Executive will commence employment with the
Company on the "EFFECTIVE DATE," which shall be no later than September 15,
2004, as mutually agreed by the Company and Executive.

            (b) Positions and Duties. As of the Effective Date, Executive will
serve as the Senior Vice President and Chief Medical Officer of the Company and
will report to the Company's Chief Executive Officer. Executive will render such
business and professional services in the performance of his duties, consistent
with Executive's position within the Company, as will reasonably be assigned to
him by the Company's Chief Executive Officer (the "CEO"). The CEO may modify
Executive's job duties, and the Company's Board of Directors (the "BOARD") may
modify Executive's title, as they deem necessary and appropriate in light of the
Company's needs and interests from time to time. The period of Executive's
employment under this Agreement is referred to herein as the "EMPLOYMENT TERM."

            (c) Obligations. During the Employment Term, Executive will perform
his duties faithfully and to the best of his ability and will devote his full
business efforts and time to the Company. For the duration of the Employment
Term, Executive agrees not to actively engage in any other employment,
occupation or consulting activity for any direct or indirect remuneration
without the prior approval of the CEO.

      2. At-Will Employment. The parties agree that Executive's employment with
the Company will be "at-will" employment and may be terminated at any time with
or without cause or notice. Executive understands and agrees that neither his
job performance nor promotions, commendations, bonuses or the like from the
Company give rise to or in any way serve as the basis for modification,
amendment, or extension, by implication or otherwise, of his employment with the
Company.

      3. Compensation.

            (a) Base Salary. During the Employment Term, the Company will pay
Executive an annual salary of $250,000 as compensation for his services (the
"BASE SALARY"). The Base Salary will be paid periodically in accordance with the
Company's normal payroll practices and be subject to the usual, required
withholding. Executive's salary will be subject to review and adjustments will
be made based upon the Company's standard practices; provided, however, that
Executive's Base Salary will not be reduced during the Employment Term unless
the Company also similarly reduces the base salaries of all other executives of
the Company.

                                       1.
<PAGE>

            (b) Bonus. Executive will be entitled to participate in any bonus
plan adopted by the Company for its employees or executive officers on such
terms as the Board may determine in its discretion, including the existing
XenoPort, Inc. Bonus Plan. Executive's target bonus under the terms of such
Bonus Plan for 2004 equals twenty percent (20%) of his Base Salary.

            (c) Stock Option. Subject to approval of the Board, Executive will
be granted a stock option, which will be, to the extent possible under the
$100,000 rule of Section 422(d) of the Internal Revenue Code of 1986, as amended
(the "CODE"), an "incentive stock option" (as defined in Section 422 of the
Code), to purchase 500,000 shares of the Company's Common Stock (as adjusted for
stock splits, stock dividends and similar events) at an exercise price equal to
the fair market value of such stock on the date of grant as determined by the
Board in its sole discretion (the "OPTION"). The Option will vest as to
twenty-five percent (25%) of the shares subject to the Option one year after the
Effective Date, and as to 1/48th of the shares subject to the Option monthly
thereafter, so that the Option will be fully vested four (4) years from the
Effective Date, subject to Executive's continued service to the Company through
the relevant vesting dates. The Option will be subject to the terms, definitions
and provisions of the Company's 1999 Stock Plan (the "OPTION PLAN") and the
stock option agreement by and between Executive and the Company (the "OPTION
AGREEMENTS"), both of which documents are incorporated herein by reference.

            (d) Housing.

               (i) Housing Search. The Company will reimburse Executive for
reasonable travel expenses for one trip by Executive and Executive's immediate
family to the San Francisco Bay Area in connection with Executive's search for a
home, in accordance with the Company's current expense reimbursement policy.

               (ii) Moving and Relocation Related Expenses. Executive will be
entitled to a cash payment intended to cover Executive's moving and relocation
related expenses (the "RELOCATION AMOUNT") in the amount of $75,000 to be paid
on or about the Effective Date, in accordance with the Company s normal payroll
practices and subject to the usual, required withholding. In the event
Executive's services to the Company terminate for any reason on or prior to the
six-month anniversary of the Effective Date, Executive will return to the
Company one hundred percent (100%) of the Relocation Amount; provided, however,
that if Executive's services to the Company are (1) terminated by the Company
without Cause (as defined below), (2) terminated by Executive for Good Reason
(as defined below) or (3) terminated due to Executive's death or disability, on
or prior to the six-month anniversary of the Effective Date, Executive shall not
be required to return any portion of the Relocation Amount.

               (iii) Housing Loan. The Company will provide Executive a loan
secured by a deed of trust on Executive's principle residence (which security
interest will be subordinate to Executive's first mortgage from a financial
institution on such residence) in a principal amount of up to $150,000 (the
"LOAN"), in order to assist Executive in the purchase of a home in the San
Francisco Bay Area. The Loan, including principal and outstanding interest
thereon, will be payable by Executive at the earlier of (i) immediately prior to
the filing by the Company of its first registration statement with the
Securities and Exchange Commission under

                                       2.
<PAGE>

the Securities Act of 1933, as amended (the "REGISTRATION STATEMENT FILING"),
(ii) immediately upon Executive's termination of services to the Company or
(iii) immediately upon the sale of the residence securing the Loan. If Executive
continues to provide services to, and be in good standing with, the Company
immediately prior to the Registration Statement Filing, the Company shall
forgive repayment of the Loan, including accrued interest thereon. In connection
with any such forgiveness of the Loan, Executive shall be entitled to receive a
cash payment (a "GROSS-UP PAYMENT") from the Company, or the Company shall pay
such amount on Executive's behalf to the applicable government agency, in the
sole discretion of the Company, in an aggregate amount sufficient to pay (i)
Executive's initial applicable federal and state personal income tax liability
as a result of any such forgiveness of the Loan (the "PRIMARY PAYMENT"), (ii)
Executive's applicable federal and state personal income tax liability on the
Primary Payment (the "SECONDARY PAYMENT") and (iii) Executive's applicable
federal and state personal income tax liability on the Secondary Payment;
provided, however, in no event shall the total Gross-Up Payment exceed $115,000.
Executive shall provide the Company with such documentation as it reasonably
requests to confirm the appropriate amount of such Gross-Up Payment and to
process the payment thereof. Executive will be responsible for any further
applicable federal and state taxes associated with any forgiven principal and
interest on the Loan. The Loan will be reflected in appropriate promissory note
and security agreement documentation, all of which documents are incorporated
herein by reference. The Loan will bear interest at the minimum rate allowed by
applicable legal and accounting regulations in order for the Company not to
suffer adverse legal and/or accounting consequences, as reasonably determined by
the Company and its advisors.

               (iv) Housing Expenses. In accordance with the Company's normal
payroll practices and subject to the usual, required withholding, the Company
will pay Executive an additional cash amount as a housing expense supplement
according to the following schedule: (1) $2,500 per month during the first year
of the Employment Term; (2) $2,250 per month during the second year of the
Employment Term; and (3) $2,000 per month during the third year of the
Employment Term. Thereafter during the Employment Term, if Executive's then
applicable annual base salary is less than $280,000, the Company will pay
Executive a monthly housing expense supplement equal to one-twelfth (1/12th) of
the difference between $280,000 and Executive's then applicable annual base
salary.

      4. Employee Benefits. During the Employment Term, Executive will be
entitled to participate in the employee benefit plans currently and hereafter
maintained by the Company of general applicability to other senior executives of
the Company. The Company reserves the right to cancel or change the benefit
plans and programs it offers to its employees at any time.

      5. Vacation. Executive will be entitled to paid vacation time in
accordance with the Company's vacation policy (including, without limitation,
its policy relation to maximum accrual), with the timing and duration of
specific vacations mutually and reasonably agreed to by the parties hereto.

      6. Expenses. The Company will reimburse Executive for reasonable travel,
entertainment or other expenses incurred by Executive in the furtherance of or
in connection with the performance of Executive's duties hereunder, in
accordance with the Company's expense reimbursement policy as in effect from
time to time.

                                       3.
<PAGE>

      7. Severance During First Three Years of Employment.

            (a) Termination for other than Cause, Death or Disability;
Resignation for Good Reason. If on or prior to the third anniversary of the
Effective Date (i) the Company terminates Executive's employment with the
Company other than for Cause (as defined herein), death or disability, or (ii)
Executive resigns from his employment with the Company for Good Reason (as
defined herein), then, subject to Section 8, Executive will be entitled to (A)
receive continuing payments of severance pay at a rate equal to his Base Salary
rate, as then in effect, payable ratably over twelve (12) months from the date
of such termination in accordance with the Company's normal payroll policies and
(B) Company-paid coverage for Executive and Executive's eligible dependents
under the Company's Benefit Plans (as defined herein) for twelve (12) months
following such termination.

            (b) Termination for Cause; Voluntary Termination. If Executive's
employment with the Company terminates voluntarily by Executive (except upon
resignation for Good Reason on or prior to the third anniversary of the
Effective Date), for Cause by the Company prior to the third anniversary of the
Effective Date, or due to Executive's death or disability, then (i) all vesting
will terminate immediately with respect to Executive's outstanding options to
purchase Common Stock and shares of restricted stock, (ii) all payments of
compensation by the Company to Executive hereunder will terminate immediately
(except as to amounts already earned), and (iii) Executive will only be eligible
for severance benefits in accordance with the Company's established policies, if
any, as then in effect.

      8. Conditions to Receipt of Severance.

            (a) Separation Agreement and Release of Claims. The receipt of any
severance pursuant to Section 7 will be subject to Executive signing and not
revoking a separation agreement and release of claims in a form reasonably
acceptable to the Company. No severance pursuant to such Section will be paid or
provided until the separation agreement and release agreement becomes effective.

            (b) Subsequent Earnings. The payment of any severance pursuant to
Section 7 (i) will be reduced by amounts earned by Executive, if any, for
employment and consulting services during the twelve (12) months following
Executive's termination of employment with the Company and (ii) notwithstanding
the immediately preceding clause (i), will cease immediately and terminate
permanently at such time as Executive commences full time employment, or a
comparable consulting engagement, entitling Executive to receive annual
compensation at a rate equal to at least eighty percent (80%) of the amount of
Executive's applicable severance payments from the Company. As a condition to
receiving any severance pursuant to Section 7, Executive agrees to provide the
Company, upon its reasonable request, with reasonable evidence of Executive's
earnings, if any, from such other sources during the twelve (12) months
following Executive's termination of employment with the Company.

      9. Change of Control Agreement. At the Effective Date, Executive and the
Company shall enter into the Change of Control Agreement in the form attached
hereto as EXHIBIT A (the "CHANGE OF CONTROL AGREEMENT").

                                       4.
<PAGE>

      10. Additional Definitions.

            (a) Benefit Plans. For purposes of this Agreement, "BENEFIT PLANS"
means plans, policies or arrangements that the Company sponsors (or participates
in) and that immediately prior to Executive's termination of employment provide
Executive and/or Executive's eligible dependents with medical, dental, and/or
vision benefits. Benefit Plans do not include any other type of benefit
(including, but not by way of limitation, disability, life insurance or
retirement benefits). A requirement that the Company provide Executive and
Executive's eligible dependents with coverage under the Benefit Plans will not
be satisfied unless the coverage is no less favorable than that provided to
Executive and Executive's eligible dependents immediately prior to Executive's
termination of employment. The Company may, at its option, satisfy any
requirement that the Company provide coverage under any Benefit Plan by (i)
reimbursing Executive's premiums under Title X of the Consolidated Budget
Reconciliation Act of 1985, as amended ("COBRA") after Executive has properly
elected continuation coverage under COBRA (in which case Executive will be
solely responsible for electing such coverage for his and his eligible
dependents), or (ii) providing coverage under a separate plan or plans providing
coverage that is no less favorable or by paying Executive a lump-sum payment
which is, on an after-tax basis, sufficient to provide Executive and Executive's
eligible dependents with equivalent coverage under a third party plan that is
reasonably available to Executive and Executive's eligible dependents.

            (b) Cause. For purposes of this Agreement, "CAUSE" means either (i)
any act of personal dishonesty taken by Executive in connection with his
responsibilities as an Executive and intended to result in substantial personal
enrichment of Executive, (ii) the conviction of a felony, (iii) a willful act by
Executive which constitutes gross misconduct and which is injurious to the
Company, or (iv) following delivery to Executive of a written demand for
performance from the Company which describes the basis for the Company's belief
that Executive has not substantially performed his duties, continued violations
by Executive of Executive's obligations to the Company which are demonstrably
willful and deliberate on the Executive's part.

            (c) Good Reason. For the purposes of this Agreement, "GOOD REASON"
means without Executive's express written consent: (i) a material reduction of
Executive's duties, position or responsibilities, or the removal of Executive
from such position and responsibilities, unless Executive is provided with a
comparable position (i.e., a position of equal or greater organizational level,
duties, authority, compensation and status); provided, however, that a reduction
in duties, position or responsibilities solely by virtue of the Company being
acquired and made part of a larger entity (as, for example, when the Chief
Financial Officer of the Company remains as such following a change of control
of the Company but is not made the Chief Financial Officer of the acquiring
corporation) will not constitute "Good Reason"; (ii) a material reduction by the
Company in the Base Salary of Executive as in effect immediately prior to such
reduction, unless the Company also similarly reduces the base salaries of all
other executives of the Company; (iii) a material reduction by the Company in
the kind or level of employee benefits to which the Executive is entitled
immediately prior to such reduction with the result that the Executive's overall
benefits package is significantly reduced, unless the Company also similarly
reduces the employee benefits of all other executives of the Company; or (iv)
the relocation of Executive's principal place of employment to a facility or a
location more than 30 miles from the Executive's then present employment
location.

                                       5.
<PAGE>

      11. Confidential Information. Executive agrees to enter into the Company's
standard Employee Proprietary Information Agreement (the "PROPRIETARY
INFORMATION AGREEMENT") upon commencing employment hereunder.

      12. Non-Solicitation. Until the date one (1) year after the termination of
Executive's employment with the Company for any reason, Executive agrees not,
either directly or indirectly, to solicit, induce, attempt to hire, recruit,
encourage, take away, hire any employee of the Company or cause an employee to
leave his employment either to work for Executive or for any other entity or
person. Executive represents that he (i) is familiar with the foregoing covenant
not to solicit, and (ii) is fully aware of his obligations hereunder, including,
without limitation, the reasonableness of the scope of this covenant.

      13. Assignment. This Agreement will be binding upon and inure to the
benefit of (a) the heirs, executors and legal representatives of Executive upon
Executive's death and (b) any successor of the Company. Any such successor of
the Company will be deemed substituted for the Company under the terms of this
Agreement for all purposes. For this purpose, "SUCCESSOR" means any person,
firm, corporation or other business entity which at any time, whether by
purchase, merger or otherwise, directly or indirectly acquires all or
substantially all of the assets or business of the Company. None of the rights
of Executive to receive any form of compensation payable pursuant to this
Agreement may be assigned or transferred except by will or the laws of descent
and distribution. Any other attempted assignment, transfer, conveyance or other
disposition of Executive's right to compensation or other benefits will be null
and void.

      14. Notices. All notices, requests, demands and other communications
called for hereunder will be in writing and will be deemed given (i) on the date
of delivery if delivered personally, (ii) one (1) day after being sent by a well
established commercial overnight service, or (iii) four (4) days after being
mailed by registered or certified mail, return receipt requested, prepaid and
addressed to the parties or their successors at the following addresses, or at
such other addresses as the parties may later designate in writing:

                  If to the Company:

                  XenoPort, Inc.
                  3410 Central Expressway
                  Santa Clara, CA 95051
                  Attn: Chief Executive Officer

                  If to Executive:

                  at the last residential address known by the Company.

      15. Severability. In the event that any provision hereof becomes or is
declared by a court of competent jurisdiction to be illegal, unenforceable or
void, this Agreement will continue in full force and effect without said
provision.

                                       6.
<PAGE>

      16. Arbitration.

            (a) General. In consideration of Executive's service to the Company,
its promise to arbitrate all employment related disputes and Executive's receipt
of the compensation, pay raises and other benefits paid to Executive by the
Company, at present and in the future, Executive agrees that any and all
controversies, claims, or disputes with anyone (including the Company and any
employee, officer, director, shareholder or benefit plan of the Company in their
capacity as such or otherwise) arising out of, relating to, or resulting from
Executive's service to the Company under this Agreement or otherwise or the
termination of Executive's service with the Company, including any breach of
this Agreement, will be subject to binding arbitration under the Arbitration
Rules set forth in California Code of Civil Procedure Section 1280 through
1294.2, including Section 1283.05 (the "RULES") and pursuant to California law.
Disputes which Executive agrees to arbitrate, and thereby agrees to waive any
right to a trial by jury, include any statutory claims under state or federal
law, including, but not limited to, claims under Title VII of the Civil Rights
Act of 1964, the Americans with Disabilities Act of 1990, the Age Discrimination
in Employment Act of 1967, the Older Workers Benefit Protection Act, the
California Fair Employment and Housing Act, the California Labor Code, claims of
harassment, discrimination or wrongful termination and any statutory claims.
Executive further understands that this Agreement to arbitrate also applies to
any disputes that the Company may have with Executive.

            (b) Procedure. Executive agrees that any arbitration will be
administered by the American Arbitration Association ("AAA") and that a neutral
arbitrator will be selected in a manner consistent with its National Rules for
the Resolution of Employment Disputes. The arbitration proceedings will allow
for discovery according to the rules set forth in the National Rules for the
Resolution of Employment Disputes or California Code of Civil Procedure.
Executive agrees that the arbitrator will have the power to decide any motions
brought by any party to the arbitration, including motions for summary judgment
and/or adjudication and motions to dismiss and demurrers, prior to any
arbitration hearing. Executive agrees that the arbitrator will issue a written
decision on the merits. Executive also agrees that the arbitrator will have the
power to award any remedies, including attorneys' fees and costs, available
under applicable law. Executive understands the Company will pay for any
administrative or hearing fees charged by the arbitrator or AAA except that
Executive will pay the first $125.00 of any filing fees associated with any
arbitration Executive initiates. Executive agrees that the arbitrator will
administer and conduct any arbitration in a manner consistent with the Rules and
that to the extent that the AAA's National Rules for the Resolution of
Employment Disputes conflict with the Rules, the Rules will take precedence.

            (c) Remedy. Except as provided by the Rules, arbitration will be the
sole, exclusive and final remedy for any dispute between Executive and the
Company. Accordingly, except as provided for by the Rules, neither Executive nor
the Company will be permitted to pursue court action regarding claims that are
subject to arbitration. Notwithstanding, the arbitrator will not have the
authority to disregard or refuse to enforce any lawful Company policy, and the
arbitrator will not order or require the Company to adopt a policy not otherwise
required by law which the Company has not adopted.

                                       7.
<PAGE>

            (d) Availability of Injunctive Relief. In addition to the right
under the Rules to petition the court for provisional relief, Executive agrees
that any party may also petition the court for injunctive relief where either
party alleges or claims a violation of this Agreement or the Confidentiality
Agreement or any other agreement regarding trade secrets, confidential
information, nonsolicitation or Labor Code ss.2870. In the event either party
seeks injunctive relief, the prevailing party will be entitled to recover
reasonable costs and attorneys' fees.

            (e) Administrative Relief. Executive understands that this Agreement
does not prohibit Executive from pursuing an administrative claim with a local,
state or federal administrative body such as the Department of Fair Employment
and Housing, the Equal Employment Opportunity Commission or the workers'
compensation board. This Agreement does, however, preclude Executive from
pursuing court action regarding any such claim.

            (f) Voluntary Nature of Agreement. Executive acknowledges and agrees
that Executive is executing this Agreement voluntarily and without any duress or
undue influence by the Company or anyone else. Executive further acknowledges
and agrees that Executive has carefully read this Agreement and that Executive
has asked any questions needed for Executive to understand the terms,
consequences and binding effect of this Agreement and fully understand it,
including that Executive is waiving Executive's right to a jury trial. Finally,
Executive agrees that Executive has been provided an opportunity to seek the
advice of an attorney of Executive's choice before signing this Agreement.

      17. Integration. This Agreement, together with the Option Plan, the Option
Agreement, the Loan, the Change of Control Agreement and the Proprietary
Information Agreement, represent the entire agreement and understanding between
the parties as to the subject matter herein and supersedes all prior or
contemporaneous agreements whether written or oral. No waiver, alteration, or
modification of any of the provisions of this Agreement will be binding unless
in writing and signed by duly authorized representatives of the parties hereto.

      18. Waiver of Breach. The waiver of a breach of any term or provision of
this Agreement, which must be in writing, will not operate as or be construed to
be a waiver of any other previous or subsequent breach of this Agreement.

      19. Headings. All captions and section headings used in this Agreement are
for convenient reference only and do not form a part of this Agreement.

      20. Tax Withholding. All payments made pursuant to this Agreement will be
subject to withholding of applicable taxes.

      21. Governing Law. This Agreement will be governed by the laws of the
State of California (with the exception of its conflict of laws provisions).

      22. Acknowledgment. Executive acknowledges that he has had the opportunity
to discuss this matter with and obtain advice from his private attorney, has had
sufficient time to, and has carefully read and fully understands all the
provisions of this Agreement, and is knowingly and voluntarily entering into
this Agreement.

                                       8.
<PAGE>

      23. Attorney Expenses. The Company will reimburse Executive for fees and
expenses of Executive's personal attorney in connection with the negotiation and
execution of this Agreement, up to a maximum of $2,500, to be paid on or about
the Effective Date.

      24. Counterparts. This Agreement may be executed in counterparts, and each
counterpart will have the same force and effect as an original and will
constitute an effective, binding agreement on the part of each of the
undersigned.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                       9.
<PAGE>

      IN WITNESS WHEREOF, each of the parties has executed this Agreement, in
the case of the Company by their duly authorized officers, as of the day and
year first above written.

COMPANY:

XENOPORT, INC.

By: /s/ Ronald W. Barrett               Date: July 14, 2004

Title: Chief Executive Officer

EXECUTIVE

/s/ Pierre V. Tran                      Date: July 15, 2004
-------------------------------
Pierre Tran

                  [SIGNATURE PAGE TO TRAN EMPLOYMENT AGREEMENT]

                                      10.