In April 2011 it was announced that O'Donohoe had signed for another Irish province, agreeing to join Connacht for the 2011-12 season, in the process linking up with his former Ireland Under-20 coach Eric Elwood, who was now in charge of the western province. This was Connacht's first season in the Heineken Cup, and over the course of the season O'Donohoe vied with Connacht's other scrum-half, Frank Murphy, for the starting position. O'Donohoe made his debut for Connacht in the 2011–12 Pro12 on 10 September 2011, coming on from the bench against Scarlets, the same team that he had played against on his Leinster debut. O'Donohoe played his first European match for Connacht in the 2011–12 Heineken Cup, starting against English side Harlequins. In O'Donohoe's first season he made a total of 16 appearances in the Pro12, five of these coming as starts, and also started in four of Connacht's six Heineken Cup matches, coming off the bench in the other two.