Duffy will play an Irish boxer in Paul Robinson's revival of Billy Roche's play A Handful of Stars, which runs at the Battersea venue from 2 to 24 May 2014 (previews from 30 April).
Roche's 1988 drama is set in the Irish town of Wexford where ‘shotgun' weddings are outnumbered only by random acts of violence in the pool hall.
The production is part of Theatre503's Second Look series, introduced by Robinson to give "major productions to neglected modern classics".
Situated over the Latchmere pub, Theatre503 is a small theatre with a big reputation. Notable productions including the 2009 premiere of Katori Hall's The Mountaintop, which overcame competition from Jez Butterworth's Jerusalem to win the Olivier Award for Best New Play.
The 60-seat venue is a far cry from the stadiums Duffy performed in as a member of chart-toppers Boyzone, which he joined in 1993. The band released 21 singles and seven albums, resulting in 25 million record sales. He moved into acting in 2002 when he joined the cast of Coronation Street, playing Rovers Return barman Ciaran.