Los Angeles: Oscar-nominated actress Michelle Williams is reportedly dating her longtime friend Jason Segel. The unexpected new couple was photographed taking a romantic stroll after a meal at Frankie's Spuntino in Brooklyn on March 24, a magazine reported.

"They are smitten and very serious. He put his arm around her and made her laugh as they walked. They seemed very relaxed," a source said.

In another incident, "How I Met Your Mother" star Segel, 32, was snapped bonding with Matilda, Williams' 6-year-old daughter, as she went for a ride on her scooter.

The 31-year-old actress, who was previously engaged to late actor Heath Ledger and split five months before his death in 2008, was romantically linked to director Cary Fukunaga last year after her split from filmmaker Spike Jonze in 2009.