The actor, who also appeared in 7th Heaven and What About Brian, will play entrepreneur Steven Spence, according to TV Line.
It has been claimed that the character will serve as a love interest for Serena, despite actress Blake Lively saying recently that she wants her alter ego to "be single for a while".
Lost actress Andrea Gabriel has also signed on for the final season of Gossip Girl as a businesswoman from Dubai.
Meanwhile, Michelle Trachtenberg has confirmed that she will return as devious socialite Georgina Sparks.
Gossip Girl's final season is scheduled to premiere October 8 on The CW.