Hill International Inc. (HIL): James Mai’s Cornwall Capital Management Discloses Activist Stake

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No.     )*

Hill
International, Inc.

(Name of Issuer)

Common Stock, $0.0001 par value per share

(Title of Class of Securities)

431466101

(CUSIP Number)

Cornwall Capital Management LP

Attn: Ian D. Haft

570
Lexington Avenue, Suite 1001

New York, New York 10022

(917) 639-5438

With a
copy to:

Richard J. Birns, Esq.

Gibson, Dunn & Crutcher LLP

200 Park Avenue

New
York, New York 10166

(212) 351-4032

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

April 12, 2016

(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 Sections 240.13d-1(e), 240.13d-1(f) or 240.13d-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
Section 240.13d-7 for other parties to whom copies are to be sent.

*	The remainder of this cover page shall be filled out for a reporting persons initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

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).