May 7, 2019

Stewart Butterfield
Chief Executive Officer
Slack Technologies, Inc.
500 Howard Street
San Francisco, CA 94105

       Re: Slack Technologies, Inc.
           Registration Statement on Form S-1
           Filed April 26, 2019
           File No. 333-231041

Dear Mr. Butterfield:

       We have reviewed your registration statement and have the following
comments. In
some of our comments, we may ask you to provide us with information so we may
better
understand your disclosure.

       Please respond to this letter by amending your registration statement
and providing the
requested information. If you do not believe our comments apply to your facts
and
circumstances or do not believe an amendment is appropriate, please tell us why
in your
response.

       After reviewing any amendment to your registration statement and the
information you
provide in response to these comments, we may have additional comments.

Registration Statement on Form S-1

Risk Factors, page 13

1.     We note in your response letter dated May 6, 2019 that you disavow Mr.
Palihapitiya's
       comparisons of Slack to other high-profile public companies. Please
include a risk factor
       that:
         highlights the potential Section 5 violation that could result from
Mr. Palihapitiya's
           statements;
         focuses on Mr. Palihapitiya's comments and your position disavowing
comparisons of
           Slack to other high-profile public companies; and
         specifically addresses Mr. Palihapitiya's assertions that you will not
have to spend
           substantial amounts of money on sales and marketing to grow your
business.
 Stewart Butterfield
FirstName LastNameStewart Butterfield
Slack Technologies, Inc.
Comapany NameSlack Technologies, Inc.
May 7, 2019
May 7, 2019 Page 2
Page 2
FirstName LastName
RSU Sales, page 57

2.       Clarify that your estimate of the number of shares to be sold to cover
the tax withholding
         on RSUs that vest and settle contemporaneously with the opening of
trading is based upon
         the estimated opening price for the shares on the NYSE, and because
that price will not be
         known until trading commences, the share amounts are solely based upon
the most
         recently completed independent common stock valuation report. Disclose
that price.
         Further disclose that after effectiveness, but one day prior to the
commencement of
         trading on the NYSE, the company will revise its estimates of the
number of shares
         expected to be sold to fund the tax amounts based upon the NYSE's
published reference
         price.
Plan of Distribution, page 167

3.       Clarify how the role of the seven associate financial advisors differs
from your three
         principal financial advisors. Describe the "certain matters relating
to [your] listing" that
         these advisors are being engaged to advise and assist.
4.       Disclose the fair value per share derived from the latest independent
valuation report that
         Morgan Stanley and your other financial advisors will provide the DMM
prior to the
         opening of trading on the NYSE.
General

5.       Please clarify that your "10,000,000+ Worldwide Daily Active Users"
daily active users
         when first referenced in your graphics at the forefront of your
prospectus include paying
         and non-paying users. With respect to the testimonials you include
beginning on page
         105, supplementally provide us with consents for the individuals
quoted.
6.       You supplementally provided us with estimated preliminary results for
the three months
         ended April 30, 2019 that you plan to include in your next amendment.
Please ensure that
         any recent development disclosures include a balanced discussion of
both revenues and a
         measure of income. Please also include a reconciliation for any
preliminary non-GAAP
         measures presented. Please refer to Item 10(b) of Regulation S-K.
        We remind you that the company and its management are responsible for
the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action
or absence of
action by the staff.

       Refer to Rules 460 and 461 regarding requests for acceleration. Please
allow adequate
time for us to review any amendment prior to the requested effective date of
the registration
statement.
 Stewart Butterfield
Slack Technologies, Inc.
May 7, 2019
Page 3

        You may contact Lisa Etheredge, Senior Staff Accountant, at (202)
551-3424 or Robert
S. Littlepage, Accounting Branch Chief, at (202) 551-3361 if you have questions
regarding
comments on the financial statements and related matters. Please contact Joshua
Shainess,
Attorney-Adviser, at (202) 551-7951 or Larry Spirgel, Assistant Director, at
(202) 551-3815 with
any other questions.



FirstName LastNameStewart Butterfield                      Sincerely,
Comapany NameSlack Technologies, Inc.
                                                           Division of
Corporation Finance
May 7, 2019 Page 3                                         Office of
Telecommunications
FirstName LastName