The 58-year-old singer announced his retirement earlier this year citing an "unreliability" in his voice, but it appears that the draw of the stage was too much to resist.
"Last spring I mentioned to David Mirvish that I'd love to do some acting in one of his shows," Heppner revealed in a statement Wednesday.
"I never thought that he might take me seriously...Just think, I get to sail onstage again without having to drink Isolde's poison or wear Viking horns!"
Heppner will play four roles in Titianic, including Isidor Straus, a prominent U.S. politician and businessman who goes down with the ship.
Titanic's composer and lyricist, Maury Yeston, calls the casting "an absolute coup."
"[Heppner's voice] will bring a choral glory to the evening that any composer would cherish," Yeston said in a statement.
"I look forward to this moment when musical theatre can now avail itself of what has been a treasure of the opera and concert worlds."
Titanic, which is part of the Mirvish 2014-15 subscription season, will play May 20 to June 21, 2015 at Toronto's Princess of Wales Theatre.
Over his 35-year-career, Heppner performed with the world's top orchestras and at the most acclaimed opera venues — including New York's Metropolitan Opera House, London's Covent Garden and the Vienna State Opera — both in stage productions as well as in concerts or recitals.
He has also released a number of a Grammy and Juno award-winning recordings.
Returning to the stage for Titanic won't stop Heppner from hosting his CBC Radio shows Saturday Afternoon at the Opera and Backstage with Ben Heppner.