Songwriters Lynn Ahrens and Stephen Flaherty and book writer Thomas Meehan are collaborating on the project.
The creative team plans to try the musical out in Germany in the fall of 2012 and then bring it to Broadway the following spring, the Times said.
"It's been a long gestation period, but it's come to be a work that we're really proud of," Meehan told the newspaper. "There was some worry early on -- could we really make a musical out of a boxing picture? Could you make Rocky sing and dance? But when we did the reading, people were very impressed, and we're going forward."
Although Stallone is an artistic partner and producer on the project, there are no plans for him to appear in the show.