The new couple stepped out to celebrate at the Casamigos Halloween Party, held at a private residence on Friday (October 28) in Beverly Hills, Calif.
Hilary, 29, dressed up as a sexy pilgrim while Jason as dressed up as a Native American chief.
Other celebs seen at the party included Robin Thicke and girlfriend April Love Geary (as the Pretty Women couple), Jeff Probst (as Zorro) with wife Lisa Ann Russell, Ryan Seacrest (as a skeleton), David Spade, and Kevin Connolly.
10+ pictures inside of Hilary Duff and others attending the party… More Here! »