The Torchwood star is reportedly interested in taking the role of American showman PT Barnum towards the end of next year.
Jim Dale played the character on Broadway in 1980, while Michael Crawford starred in a West End production the following year.
Cameron Mackintosh has asked writer Mark Bramble to strengthen the storyline for the musical, which was based on a script he penned with Michael Stewart and Cy Coleman.
The theatre producer has also asked choreographer Rob Ashford (Evita, Guys & Dolls) to helm the project following the success of his directorial debut Parade.
Barrowman, who has judged aspiring West End stars in both How Do You Solve A Problem Like Maria? and Any Dream Will Do, is now in the early stage of negotiations for his return to the stage.
He is currently shooting the third series of Torchwood and scenes for forthcoming episodes of Doctor Who. He will also kick off a ten-date UK concert tour in April.
His spokesman told the Daily Mail: "John wants to come back to the West End and Barnum is an ideal show for him to do, but he can't sign to do it until scheduling has been sorted out."