13D Filing: Abdiel Qualified Master Fund LP and Appian Corp (APPN)

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

SCHEDULE 13D

(Rule 13d-101)

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No.     )*

Appian
Corporation

(Name of Issuer)

Class A Common Stock, $0.001 par value per share

(Title of Class of Securities)

03782L101

(CUSIP Number)

Abdiel Capital

410 Park Avenue, Suite 930

New York, NY 10022

Attn:
Colin T. Moran

Tel: (646) 496-9202

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

May 31, 2017

(Date of
Event Which Requires Filing of This Statement)

If the filing
person has previously filed a statement on Schedule 13G to report the acquisition which is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box.  ☐

Note. Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7 for
other parties to whom copies are to be sent.

The information required on the remainder of this cover page
shall not be deemed to be filed for the purpose of Section 18 of the Securities Exchange Act of 1934 (Act) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the
Act (however, see the Notes).

SCHEDULE 13D

This statement on Schedule 13D relates to the Class A common stock, $0.001
par value per share (the Common Stock), of Appian Corporation (the Issuer). The Issuers principal executive office is located at 11955 Democracy Drive, Suite 1700, Reston, VA 20190.

(a) This Schedule 13D is being filed by and on behalf of (i) Abdiel
Qualified Master Fund, LP; (ii) Abdiel Capital, LP; (iii) Abdiel Capital Management, LLC; (iv) Abdiel Capital Advisors, LP; and (v) Colin T. Moran (each, a Reporting Person and collectively, the Reporting
Persons). The Reporting Persons are making this single, joint filing and the agreement among the Reporting Persons to file jointly is attached hereto as Exhibit A. The execution and filing of such joint filing agreement shall not be construed
as an admission that the Reporting Persons are a group, or have agreed to act as a group.

(b) The principal business address of each Reporting Person is
410 Park Avenue, Suite 930, New York, NY 10022.

(c) Each of Abdiel Qualified Master Fund, LP and Abdiel Capital, LP is a private investment partnership,
the principal business of which is to make investments. The principal business of Abdiel Capital Management, LLC is to act as the general partner of Abdiel Qualified Master Fund, LP and Abdiel Capital, LP. The principal business of Abdiel Capital
Advisors, LP is to act as the investment manager of Abdiel Qualified Master Fund, LP and Abdiel Capital, LP. Colin T. Moran serves as managing member of Abdiel Capital Management, LLC and Abdiel Capital Partners, LLC, which serves as the general
partner of Abdiel Capital Advisors, LP.

(d)-(e) During the last five years, no Reporting Person has (i) been convicted in any criminal proceeding
(excluding traffic violations or similar misdemeanors) or (ii) been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction resulting in its being subject to a judgment, decree or final order enjoining
future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

(f) Abdiel Qualified Master Fund, LP is a Cayman Islands limited partnership, each of Abdiel Capital, LP and Abdiel Capital Advisors, LP is a Delaware limited
partnership, Abdiel Capital Management, LLC is a Delaware limited liability company, and Colin T. Moran is citizen of the United States.

In a series of transactions completed through
June 12, 2017, the Reporting Persons acquired an aggregate amount of 1,968,311 shares of Common Stock for the accounts of Abdiel Qualified Master Fund, LP and Abdiel Capital, LP for aggregate consideration of approximately $29.3
million (including commissions). The source of funds used to acquire the 1,968,311 shares of Common Stock was the working capital of Abdiel Qualified Master Fund, LP and Abdiel Capital, LP.

Except as set forth herein, the Reporting Persons do not have present plans or
proposals that relate to or would result in any of the transactions described in subparagraphs (a) through (j) of Item 4 of Schedule 13D. However, the Reporting Persons expect to evaluate on an ongoing basis the Issuers financial
condition, business, operations and prospects, conditions in the securities markets, general economic and industry conditions and other factors and may, from time to time, also engage in discussions with management and the board of directors of the
Issuer about their investment, the business, operations, governance, strategy, capitalization, ownership and future plans of the Issuer and the management and board composition of the Issuer or commercial or strategic transactions with, or relating,
to the Issuer. Depending on various factors including, without limitation, the Issuers financial position, strategic direction, business and prospects, anticipated future developments, existing and anticipated market conditions from time to
time, actions taken by the management and board of directors of the Issuer, price levels of the Common Stock, general economic conditions and regulatory matters, the Reporting Persons may in the future take such actions with respect to its
investment in the Issuer as it deems appropriate including, without limitation, purchasing additional Common Stock or other securities of the Issuer, selling some or all of their Common Stock or engaging in short selling of or any hedging or similar
transaction with respect to the Common Stock, to the extent permitted under applicable law.

(a) The information requested by this paragraph is incorporated
herein by reference to the information provided on the cover pages to this Schedule 13D.

(b) The information requested by this paragraph is incorporated
herein by reference to the information provided on the cover pages to and Item 2(c) of this Schedule 13D.

(c) Information with respect to all
transactions in the Common Stock which were effected during the past sixty days by each of the Reporting Persons is set forth on Exhibit B attached hereto and incorporated herein by reference.

(d) No other person has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the shares of Common
Stock set forth above.

(e) Not applicable.

Not
applicable.

Exhibit A – Joint Filing Agreement

Exhibit B – Information with respect to Transactions Effected During the Past Sixty Days

SIGNATURES

After reasonable inquiry and to the best of their knowledge and belief, the undersigned certify that the information set forth in this statement is true,
complete and correct.

Dated: June 12, 2017