The moustached former OC star – who will forever be Seth Cohen for many - went casual at the screening, teaming white trousers with a pattered blue shirt.
He was without pregnant wife Leighton Meester, which isn't that much of a surprise considering they like to keep their relationship away from the spotlight.
They are expecting their first child later this year.
Sleeping With Other People is a comedy about a womanizer (Jason Sudeikis) who forms a friendship with a serial cheater (Alison Brie). It's scheduled for release in the UK in January.