Morrison will play Evan in the film that will be released in May 2012. When he is paired with Diaz's character, Jules, on a celebrity dance show, things begin to heat up on and off the dance floor, leading to a pregnancy which forces the couple to re-evaluate what's important in life.
Kirk Jones directs the film, which is based on Heidi Murkoff's best-selling book. The cast also includes Anna Kendrick, Jennifer Lopez, Brooklyn Decker, Elizabeth Banks, Chace Crawford and Rob Huebel.
Morrison was nominated for a Tony Award in 2005 for his performance in The Light in the Piazza and currently stars as Will Scheuster on the Fox hit series "Glee," the new season of which begins Sept. 20.