<PAGE>
 
                                                                   EXHIBIT 10.13

                             EMPLOYMENT AGREEMENT


Agreement made, effective as of April 24, 1997, by and between Internet
Communications Corporation, a Colorado corporation, hereinafter referred to as
employer, and Timothy A. Griffin, hereinafter referred to as employee.

                                   RECITALS

The parties recite and declare:

     A.   Employer is engaged in the business of selling full service voice and
          data communications products and services at 7100 East Belleview
          Avenue, Suite 201, Greenwood Village, Colorado, 80111.

     B.   Employee is desirous of performing services as an employee for
          employer in such business under the terms hereof.

     C.   Employer is willing to employ employee, upon the terms, covenants, and
          conditions set forth in this agreement.

For the reasons set forth above, and in consideration of the mutual promises and
agreements set forth in this agreement, employer and employee agree as follows:

                                1.  EMPLOYMENT

     A.   Employer hereby employs employee as Vice President, General Manager to
                                              -------------------------------
perform business management activities and employee hereby accepts and agrees to
such employment, subject to the general supervision and pursuant to the orders,
advice, and direction of employer.

     B.   Employee shall perform such other duties as are customarily performed
by one holding such position in similar businesses as that engaged in by
employer, and shall also render such unrelated services and duties as may be
assigned to him/her from time to time by employer.

                         2.  BEST EFFORTS OF EMPLOYEE

     Employee agrees that he/she will at all times faithfully, industriously,
and to the best of his/her ability, experience, and talents, perform all of the
duties that may be required of and from him/her pursuant to the express and
implied terms of this agreement, to the reasonable satisfaction of employer.
Such duties shall be rendered at 7100 East Belleview Avenue, City of Greenwood
Village, State of Colorado, and at such other place or places as employer shall
in good faith require or as the interest, needs, business or opportunities of
employer shall require.

                         3.  COMPENSATION OF EMPLOYEE

     Employer shall pay employee, and employee shall accept from employer, in
payment for employee's services under this agreement, base compensation at the
rate of One Hundred Fifteen Thousand Dollars ($115,000) per year, payable twice
        ----------------------------          --------
a month on the 15th and last day of each month while this agreement is in force.

     Employer shall reimburse employee for all necessary expenses incurred by
employee while traveling pursuant to employer's direction.

                                       1
<PAGE>
 
                                                                   EXHIBIT 10.13

                       4.  OTHER EMPLOYMENT DURING TERM

     Employee shall devote all of his/her time, attention, knowledge, and skills
solely to the business and interest of employer, and employer shall be entitled
to all of the benefits and profits arising from or incident to all work,
services, and advice of employee, and employee shall not, during the term of
this agreement, be interested directly or indirectly, in any manner, as partner,
officer, director, owner, shareholder, advisor, employee, or in any other
capacity in any other business similar to employer's business or any allied
trade; provided, however, that nothing contained in this section shall be deemed
to prevent or to limit the right of employee to invest any of his/her money in
the capital stock or other securities of any corporation whose stock or
securities are publicly owned or are regularly traded on any public exchange.

                     5.  NON-COMPETITION AFTER TERMINATION

     Employee agrees that, in addition to any other limitation herein, for a
period of two years after the termination of his/her employment under this
agreement, and unless otherwise specified in this agreement, employee will not
directly or indirectly engage in, or in any manner be connected with or employed
by any person, firm, corporation, or other entity in competition with employer
or within a radius of 100 miles of any office of employer, its affiliates or its
subsidiaries.

                      6.  SOLICITATION AFTER TERMINATION

          Employee agrees that, in addition to any other limitation, for a
period of two years after the termination of his/her employment under this
agreement, and unless otherwise specified in this agreement, employee will not,
on behalf of himself/herself or on behalf of any other person, firm,
corporation, or other entity, call on any of the customers of employer, or any
of its affiliates or subsidiaries for the purpose of soliciting and/or providing
to any of such customers any voice and data communication products and services,
nor will he/she in any way, directly or indirectly, for himself/herself, or on
behalf of any other person, firm, corporation, or other entity solicit, divert,
or take away any customer of employer, its affiliates or its subsidiaries.

                 7.  RECOMMENDATIONS FOR IMPROVING OPERATIONS

     Employee shall make known to employer all information of which employee
shall have any knowledge and shall make all suggestions and recommendations that
will be of mutual benefit to employer and employee.  Employee acknowledges that
all work performed by him/her during the term of this agreement is the property
of employer and that upon termination of employment, he/she will promptly supply
employer with all notes, memoranda, files, reports, customer lists and other
lists, correspondence, technical data, and any other tangible product or
document which the employee produced, received, or otherwise had access to while
employed.

                               8.  TRADE SECRETS

     Employee shall not at any time, either directly or indirectly, divulge,
disclose or communicate to any person, firm, corporation, or other entity in any
manner whatsoever any information concerning any matters affecting or relating
to the business of employer, including without limitation, the identity of its
customers and prospective customers, their communication systems, needs,
preferences and personnel, the prices it obtains or has obtained from the sale
of, or at which it sells or has sold, its products and services, marketing
strategies, product development, financing, expansions, business policies and
practices or any other information concerning the business of employer, it's
manner of operation, its plans, processes, or other data without regard to
whether all of the above-stated matters will be deemed confidential, material,
or important, employer and employee specifically and expressly stipulating that
as between them such matters are important, material, and confidential and
gravely affect the effective and successful conduct of the business of employer,
and employer's good will, and that any breach of the terms of this section shall
be a material breach of this agreement.

                                       2
<PAGE>
 
                                                                   EXHIBIT 10.13

                 9.  INJUNCTIVE RELIEF AND LIQUIDATED DAMAGES

     Employee hereby agrees that for violation of any of the provisions of this
agreement, employer shall, in addition to any other rights and remedies
available under this agreement, at law or otherwise, be entitled to an
injunction to be issued by any court of competent jurisdiction enjoining and
restricting employee from committing any violation of the agreement and employee
hereby consents to the issuance of such injunction.

                      10.  AGREEMENTS OUTSIDE OF CONTRACT

     This agreement contains the complete agreement concerning the employment
arrangement between the parties and shall, as of the effective date hereof,
supersede all other arrangements between the parties.  The parties stipulate
that neither of them has made any representation with respect to the subject
matter of this agreement except such representations as are specifically set
forth in this agreement and each of the parties acknowledges that he/she or it
has relied on its own judgment in entering in to this agreement.  The parties
further acknowledge that any payments or representations that may have been made
by either of them to the other prior to the date of executing this agreement are
of no effect an that neither of them has relied thereon in connection with
his/her or it's dealings with the other.

                        11.  MODIFICATION OF AGREEMENT

     Any modification of this agreement or additional obligation assumed by
either party in connection with this agreement shall be binding only if
evidenced by a writing signed by each party or an authorized representative of
each party.

                               12.  TERMINATION

     A.   Employee's employment may be terminated without cause by either party
on sixty (60) calendar days written notice to the other.  In such event,
employee shall be entitled to compensation for such sixty (60) days provided
he/she continue to perform his/her services during such period.

     B.   In the event that employee is terminated for felonious or fraudulent
reasons, such as embezzlement or other theft of company property, employer may
terminate employment without notice and with compensation to employee only to
the date of such termination.

     C.   In the event of any violation by employee of any of the terms of this
agreement, employer may terminate employment without notice and with
compensation to employee only to the date of such termination

     D.   It is further agreed that any breach or evasion of any of the terms of
this agreement by either party will result in immediate and irreparable injury
to the other party and will authorize recourse to injunction and or specific
performance as well as to all other legal or equitable remedies to which such
injured party may be entitled under this agreement.

     E.   In the event the employer chooses to terminate the employee with or
without cause the above section 5 will no longer be valid.


                       13.  EFFECT OF PARTIAL INVALIDITY

     The invalidity of any portion of this agreement will not and shall not be
deemed to affect the validity of any other provision.  In the event that any
provision of this agreement is held to be invalid, the parties agree that the
remaining provisions shall be deemed to be in full force and effect as if they
had been executed by both parties subsequent to the expungement of the invalid
provision.

                              14.  CHOICE OF LAW

                                       3
<PAGE>
 
                                                                   EXHIBIT 10.13

     It is agreed that this agreement shall be governed by, construed and
enforced in accordance with the laws of the State of Colorado.

                                15.  NO WAIVER

     The failure of either party to this agreement to insist upon the
performance of any of its terms and conditions or the waiver of any breach of
any of its terms and conditions shall not be construed as thereafter waiving any
such terms and conditions, but the same shall continue and remain in full force
and effect as if no such forbearance or waiver had occurred.

                            16.  PARAGRAPH HEADINGS

     The titles to the paragraphs of this agreement are solely for the
convenience of the parties and shall not be used to explain, modify, simplify,
or aid in the interpretation of the provisions of this agreement.

                              17.  BINDING EFFECT

     This agreement shall be binding on and shall insure to the benefit of any
successor or successors of employer and the personal representatives of
employee.


     In witness whereof, each party to this agreement has caused it to be
executed at 7100 E. Belleview Avenue, Suite 201, Greenwood Village, Colorado,
            -----------------------------------------------------------------
80111 on the date indicated below.
-----                             



INTERNET COMMUNICATIONS CORPORATION



By:   /s/ Thomas C. Galley
   ---------------------------------
      Employer


      /s/ Timothy A. Griffin
------------------------------------
      Employee


      May 15, 1997
 -----------------------------------
      Date

                                       4