The Grey's Anatomy star will appear alongside Renee Zellweger and Colin Firth in the third instalment in the hit franchise, which is called Bridget Jones' Baby.
It's his first major role since leaving Grey's Anatomy.
Details about the plot are hazy but it's believed the movie will not follow the plotline of the third Bridget Jones book, Mad About A Boy, and instead be a fresh screenplay with input from author Helen Fielding, telling what happened between the second and third books.
Renee reprises her role as 30-something publisher Bridget, while Colin returns as her handsome lawyer lover Mark Darcy. Hugh Grant will not return as Bridget's ex-boss Daniel Cleaver.
Filming starts 2 October in UK.
It's eleven years since we last saw Bridget on our screens in The Edge of Reason, which followed her new TV career, blossoming relationship with Mark and unfortunate stint in a Thai prison.