Director Adam Shankman ("Hairspray") confirmed the "30 Rock" actor's inclusion in the cast via Twitter on Friday.
"Based on info I got today," Shankman wrote on the microblogging site. "I'm gonna confirm Alec Baldwin as Dennis in 'Rock Of Ages.' Hollah."
Baldwin will be playing the role of Dennis Dupree, an ex-rocker who runs the Rock of Ages nightclub and can't let go of the past.
On Thursday, it was confirmed that "Dancing With the Stars" professional Hough would play opposite Cruise as Sherrie, a small-town girl who catches the eye of Cruise's character Stacee Jaxx, a rock star at the top of his career. Hough may also be seen in some provocative outfits since the character of Sherrie becomes a stripper.
Mary J. Blige has also signed on to the project to play a character called Justice. The film will be based off the hit Broadway musical which featured classic 80s hair rock hits from bands like Journey, Bon Jovi, and Twisted Sister. Cruise's character is expected to sing Bon Jovi's "Wanted Dead or Alive." The character is also a part of other numbers including Foreigner's "I Wanna Know What Love Is." The Broadway musical starred "American Idol" alum Constantine Maroulis.
The film is slated to begin shooting in May. Russell Brand is also rumored to be joining the cast.
In February, Baldwin received a star on Hollywood's Walk of Fame, shortly before "30 Rock" shot their 100th episode. His role on the show as network executive Jack Donaghy has earned Baldwin two Emmy Awards.
Baldwin rose to fame in the 1980s as a television actor and later filmed movies such as the 1988 cult classic "Beetlejuice" and the 2003 film "The Cooler," the latter of which earned him an Oscar nomination.
Baldwin told Men's Journal in 2009 that he considers his "entire movie career a complete failure." He said last month that he is "very, very interested" in going into politics, but denied in January that he would be replacing Keith Olbermann on MSNBC.
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