<PAGE>
                                                            Exhibit 10(iii)A(59)


                                                 March 28, 2000



Mr. James H. Heagle
520 Salem Heights Drive
Gibsonia, Pennsylvania   15044


Dear Jim:


      This letter will confirm the terms of your employment by National Service
Industries, Inc. ("NSI"), effective May 1, 2000 (the "Effective Date"). We are
enthusiastic about your decision to join NSI and look forward to working with
you to build a bigger, stronger NSI.

      The terms of your employment will be as follows:

      1.    Title and Duties - As President, NSI Chemicals, you will report to
George Gilmore, Executive Vice President and Group President. You will have
responsibility for NSI Chemicals business and any other duties consistent with
your position which may be assigned to you by Mr. Gilmore. You will devote
substantially all of your working time and attention to the business and affairs
of NSI Chemicals.

      2.    Base Salary - Your base salary will be Twenty-five Thousand Dollars
($25,000) per month or the equivalent annual rate of Three Hundred Thousand
Dollars ($300,000), subject to review for increases. In addition, you will
receive a signing bonus of Ten Thousand Dollars ($10,000) payable within thirty
(30) days after the Effective Date.

      3.    Annual Incentive Compensation - You will participate in the NSI
Management Compensation and Incentive Plan (the "AIP") for the fiscal year
beginning September 1, 2000 with a target bonus equal to 45% of your base
salary. You will participate in the AIP for the fiscal year ending August 31,
2000 on a pro rata basis for the period of your employment.

      4.    Long-Term Achievement Incentive Plan - You will receive a grant of
employee stock options for ten thousand (10,000) shares of stock under our
current long-
<PAGE>
Page 2
J.H. Heagle
March 28, 2000


term incentive plan upon your arrival at NSI. You will also be entitled to
participate in the current long-term incentive plan on a prorated basis for the
number of months you are employed with NSI during the remainder of the
three-year cycle ending August 31, 2001 and the remainder of the three-year
cycle ending August 31, 2002 based on the performance of NSI's Chemical Group.
In addition, you will participate in the Plan for the three-year cycle beginning
September 1, 2000 on a comparable basis with operating unit presidents. This
Plan provides for annual grants of stock options and annual "aspiration awards"
having a total value equal to 160% of salary at commitment (or target) level
performance. Stock options represent 30% of total value (or 48% of salary) and
aspiration awards represent 70% of total value (or 112% of salary) at commitment
level performance. The payout for aspiration awards for aspiration level
performance is equal to five times the value of the payout for commitment level
performance (or 560% of salary). Failure to achieve threshold level performance
will result in no payout.

      5.    Retirement Plans - Upon satisfying the eligibility requirements, you
will be eligible to participate in NSI's tax-qualified retirement plans, NSI
Pension Plan C, and the NSI 401(k) Plan for Corporate Office Employees. In
addition, upon employment, you will become a participant in the Supplemental
Pension Plan for National Service Industries, Inc. (the "SPP").

      6.    Medical, Life Insurance, and Other Employee Benefits - You will be
covered by, or eligible to participate in, the medical, dental, life insurance,
disability, deferred compensation, and other benefit programs generally made
available by NSI to its operating unit presidents and their families, including
a car allowance of Four Hundred Dollars ($400) per month. We will reimburse you
for your COBRA expenses until you are covered under our program. You will be
eligible to participate in NSI's financial planning program. You will also be
entitled to four (4) weeks vacation per calendar year.

      7.    Relocation Expenses - NSI will pay the following relocation
expenses:

            (a)   your expenses for moving your household effects to Atlanta;

            (b)   rent for an apartment and storage of your personal effects in
                  Atlanta, pending your move into your new home in Atlanta on or
                  before February 1, 2001;

            (c)   brokerage and closing costs (up to two points) you incur in
                  connection with the sale of your home in Gibsonia and the
                  purchase of a home in
<PAGE>
Page 3
J.H. Heagle
March 28, 2000


                  Atlanta;

            (d)   reasonable travel expenses to and from Gibsonia for you and
                  your wife and children until you have moved your residence to
                  Atlanta; and

            (e)   a one-time payment of one month's salary for your assistance
                  in the relocation.

The foregoing payments will be "grossed up" so that, to the extent reasonably
practicable, they will represent your after-tax cost for covered expenses. In
addition to the foregoing, we will assist you in obtaining a bridge loan should
you purchase a home in Atlanta before selling your home in Gibsonia. As we
discussed, you will put your home in Gibsonia on the market within ninety (90)
days after the Effective Date. If you have not sold your home by February 1,
2001, NSI will engage a home buying service to purchase your home.

      8.    Employment at Will/Severance Payment/Change in Control - Your
employment will be at will and may be terminated by either NSI or you at any
time for any reason, with or without notice. Except in the event of termination
in connection with a Change in Control of NSI (as defined in the Severance
Protection Agreement that will cover you), you will be entitled to the following
severance payment:

            -     If your employment is terminated for any reason other than
                  voluntary termination, termination upon death or Disability
                  (as defined below), or termination by NSI for Cause (as
                  defined below), you will receive a severance payment (payable
                  in semi-monthly installments) equal to your then current
                  salary for a period of twelve (12) months, subject to your
                  execution of a release and severance agreement in a form
                  acceptable to both parties.

For purposes of entitlement to a severance benefit, "Cause" shall mean any
act(s) on your part that constitutes fraud, a felony involving dishonesty, a
breach of fiduciary duty, insubordination, or gross malfeasance or habitual
neglect of your duties for NSI, and "Disability" shall mean a physical or mental
infirmity which impairs your ability to substantially perform your duties as
President, NSI Chemicals with or without reasonable accommodation for a period
of one hundred eighty (180) consecutive days.

With respect to Change in Control situations, you will be covered by a Severance
Protection Agreement with the same provisions as are applicable to NSI's
operating unit
<PAGE>
Page 4
J.H. Heagle
March 28, 2000


presidents. In the event of your termination in connection with a Change in
Control that entitles you to benefits under the Severance Protection Agreement,
you will receive the greater of the payments and benefits provided under the
Severance Protection Agreement (after consideration of any tax penalties) or the
severance payments described above.

      9.    Relocation of Residence to Atlanta - You will relocate your
residence to Atlanta and complete the move of your family on or before February
1, 2001.

      The base salary, annual incentive, long-term incentives, nonqualified
retirement benefits, and any severance payments will be structured to ensure the
tax deductibility to NSI of the payments and benefits under the Internal Revenue
Code of 1986. We can provide additional information on these issues if you so
desire.

      We will prepare an SPP amendment and Severance Protection Agreement to
evidence the arrangements set forth in this letter.

      We are delighted you are joining NSI and we look forward to a long and
mutually satisfactory relationship. This letter outlines your employment
relationship with NSI; if you agree with the employment terms as outlined above,
please sign and date both copies of this letter agreement and return one copy to
me at your earliest convenience.

                                            Sincerely,



                                            /s/ George H. Gilmore, Jr.
                                            George H. Gilmore Jr.


ACCEPTED AND AGREED TO THIS

_____ DAY OF _____________, 2000



/s/ James H. Heagle
    James H. Heagle