He was nominated for the 2015 Munster Rugby Senior Player of the Year Award in April 2015. O'Donnell won his 100th cap for Munster on 25 April 2015, scoring a try in the 30–19 win against Benetton and winning the Man-of-the-Match award. He was named in the 2014–15 Pro12 Dream Team, alongside teammate CJ Stander. In December 2015, O'Donnell signed a three-year contract with Munster. On 27 December 2015, O'Donnell made his return from the injury he sustained during the World Cup with Ireland, coming off the bench against Leinster during a 2015–16 Pro12 game.