The actor, who played Harper in the CW show's first season, has been cast as Maya (Bianca Lawson)'s cousin Nathan St. Germain.
The character is studying law and soon becomes "catnip to most members of the opposite sex" at Hollis College, according to TV Guide.
Sulieman previously appeared in the eighth and final season of 24, as well as the likes of Bones, Entourage and Perfect Couples.
The third season of Pretty Little Liars is scheduled to premiere on ABC Family on June 5.
A trailer for the new episodes was released in March.