The Die Hard star was rumoured to be in negotiations for the film earlier this week, and co-star Dwayne 'The Rock' Johnson has now confirmed his involvement.
"Welcome brother Bruce Willis to the cast of G.I. Joe," Johnson tweeted this weekend. "What an honour."
Willis will now portray the first G.I. General Joe Colton opposite returning stars Channing Tatum and Ray Park.
Johnson will star in the film as Roadblock opposite several other newcomers including Elodie Yung as Jinx, Adrianne Palicki as Lady Jaye, RZA as the Blind Master, Joseph Mazello as Mouse and Rome star Ray Stevenson as Firefly.
G.I. Joe 2 is expected to begin production later this month for release on June 29, 2012.
Watch the trailer for G.I Joe: The Rise of Cobra below: