Jason Segel has confirmed he is dating Michelle Williams.

The Five-Year Engagement star was first photographed with Dawson's Creek alum last month, and has now confirmed they are indeed an item.

"I think we would just very much like to be happy. That's all I'm going to say about it," he said when Extra asked about their romance.

His current co-star and off-screen friend Emily Blunt jokes that the 32-year-old actor has significantly matured thanks to Michelle: "He's a man-boy! He used to be a boy-boy and now he's a man-boy."

"I think I might even be becoming a man-man ... potentially!" Jason added.

Michelle knew Jason for years through mutual friend Busy Philips, before their romance, "kind of happened overnight," according to US Weekly. A source says Jason has been making a conscious effort to behave more maturely to show his "commitment" to Michelle.