Jason Segel and Michelle Williams have kept their new romance fairly private, but the couple finally made their public debut on Wednesday, at the New York premiere of Segel's film The Five-Year Engagement.

While the couple did not pose for photos together, People magazine reports that Segel and Williams were affectionate during the screening and after party, held at the Museum of Modern Art.

Segel, 32, reportedly took Williams, 31, around the party from table to table, before the latter checked out for the night.

The premiere, which officially opened the 11th Tribeca Film Festival, also saw the faces of Segel's Five-Year Engagement co-star Emily Blunt, producer Judd Apatow, festival co-founder Robert De Niro and festival juror Leelee Sobieski, who could barely contain her excitement for the new couple.

I just think it's really sweet . . . it makes me happy too. I think it makes everybody happy. When everybody blesses a union between two people for some reason, it's great! The whole world sending a positive energy for two people to be happy. That's nice, Sobieski told The Hollywood Reporter.

Segel and Williams first made romantic headlines some three weeks ago, when they were spotted walking hand in hand in Brooklyn after a dinner date.

He put his arm around her and made her laugh as they walked . . . [they] seemed very relaxed, a source told Us Weekly.

The very next day, Segel was spotted in Brooklyn taking a different stroll, this time with Williams' 6-year-old daughter Matilda.

Last weekend, the How I Met Your Mother star was spotted holding an iPhone with taped photos of Williams blowing what appears to be I Love You kisses, further hinting at his new relationship.

When asked about Williams during a recent press junket for The Five-Year Engagement though, Segel stayed mum.

I think I would just very much like to be happy . . . that's all I'm going to say about it, he told Extra.

Williams, whose last high-profile relationship was with the late Heath Ledger, has actually known Segel for many years, through his Freaks and Geeks co-star Busy Phillips. Phillips, who met Williams on the set of Dawson's Creek, is also the godmother of Matilda.

The Five-Year Engagement opens Apr. 27.