For the 2011–12 season, Connacht qualified for the Heineken Cup, Europe's premier club rugby competition, for the first ever time, and Muldoon's Galwegians club mate and fellow Ireland cap-holder, Gavin Duffy, was made team captain. The start of the season also saw the Celtic League renamed, becoming the Pro12. In the first Pro12 season, Muldoon played in every one of Connacht's 22 games, starting all but two of them. Muldoon played his first ever Heineken Cup game on 11 November 2011, against Harlequins in the Stoop. He started all six of the team's games including the bonus point defeats to Gloucester and the victory over Harlequins in the return leg in Galway, which was Connacht's first ever Heineken Cup win.