The Boyzone singer - who has recently been working as a judge on the Australian version of `The X Factor` - will return Down Under next month to shoot scenes for the top secret project.
Asked when he plans to return to Oz, 34-year-old Ronan told 2Day FM`s `Kyle and Jackie O Show`: "I`m coming down on April 7, because I`m shooting my first movie in Australia. I just gave you a world exclusive actually.
"I can`t tell you the title but I`m going to be on set on April 10 in Sydney.
"It`s an Australian movie ... I`m very excited."
Ronan - who has three children, Jack, Marie and Ali, with his wife Yvonne - previously revealed he auditioned for a role in upcoming fantasy prequel `The Hobbit` and was keen to launch a film career.
He said: "I don`t think I`ll get the role of the hobbit. But I would like to take on roles which nobody would expect. I don`t want to be reduced to love stories. I`d like to try dark, edgy roles. I need a challenge."