The 26-year-old former X Factor winner will play rock star Stacee Jaxx in the musical, which will also feature Justin Lee Collins as nightclub owner Dennis Dupree.
Ward said in a statement: "I cannot wait to take to the stage for Rock of Ages.
"It's an absolute thrill to have been chosen for this part and can't wait to show a new side to my voice."
The 'Gotta Be Somebody' singer later added on Twitter: "I'm proud to announce that I will be in the hit musical @rockofagesuk as 'STACEE JAXX'.
"I'm sooooo excited #Letsrock... Thankyou to everyones kind messages. I really cant wait to hit the stage (sic)."
Previews of the musical, which uses 1980s classic rock anthems from Bon Jovi, Journey and others as its soundtrack, start in August at the Shaftesbury Theatre.
Rock of Ages will receive its official premiere in September.
A film version of Rock of Ages is currently in production, directed by Adam Shankman (Hairspray). The ensemble cast includes Alec Baldwin, Catherine Zeta-Jones and Russell Brand.
Tom Cruise will play the role of Jaxx in the movie, which is due for release next year.