Walken will play the role of Angelo "Gyp" DeCarlo, the part originated on Broadway by Mark Lotito.
Variety previously reported that Eastwood and his producers are currently eyeing John Lloyd Young, Erich Bergen, Michael Lomenda and Vincent Piazza for the film's lead roles. All but Piazza, a star of TV's "Boardwalk Empire," have performed in some version of the Tony-winning musical.
The film will begin shooting late this summer in Los Angeles. Graham King ("Argo") and Robert Lorenz ("Million Dollar Baby") are producing the film.
As previously reported, Tony Award-winning playwright John Logan (Red, I'll Eat You Last) has penned the screenplay based on the original Broadway script written by Marshall Brickman and Rick Elice, who earned Tony Award nominations for their work.
The film will include the hit songs from the Broadway production by Bob Gaudio and Bob Crewe.
The musical opened at the August Wilson Theatre on Broadway to critical acclaim on Nov. 6, 2005.
Jersey Boys is the winner of the 2006 Best Musical Tony Award, the 2006 Grammy Award for Best Musical Show Album, the 2009 Olivier Award for Best New Musical and the 2010 Helpmann Award for Best Musical (Australia).
Jersey Boys is the story of Frankie Valli and The Four Seasons: Frankie Valli, Bob Gaudio, Tommy DeVito and Nick Massi. According to press notes, "This is the story of how a group of blue-collar boys from the wrong side of the tracks became one of the biggest American pop music sensations of all time. They wrote their own songs, invented their own sounds and sold 175 million records worldwide - all before they were thirty."