FILE - In this Nov. 23, 2011 file photo, actor Jason Segel arrives at the premiere of The Muppets at El Capitan Theater in Los Angeles. The Hasty Pudding Theatricals of Harvard University announced that Segel will be the recipients of its 2012 Man of the Year award. The Man of the Year festivities will take place on Feb. 3. (AP Photo/Katy Winn, file)

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.

Asked about their romance by US television show ‘Extra’, he said: "I think we would just very much like to be happy. That's all I'm going to say about it."

His current co-star and off-screen friend Emily Blunt jokes that the 32-year-old actor has significantly matured thanks to Michelle.

She said: "He's a man-boy! He used to be a boy-boy and now he's a man-boy." Jason added, "I think I might even be becoming a man-man ... potentially!"

Michelle – who has daughter Matilda, six, from her previous relationship with the late Heath Ledger – 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.

The insider said: “[Jason] has been trying to be more of a grown-up lately.

"He is taking care of himself more, exercising, eating right and dressing better. Basically, not acting like a frat boy anymore." - Bang Showbiz