On 20 January 2016, O'Donnell was named in Ireland's 35-man squad for the 2016 Six Nations Championship. On 7 February 2016, O'Donnell started against Wales in Ireland's opening match of the Six Nations. On 13 February 2016, O'Donnell came off the bench against France to replace Seán O'Brien after he went off injured. On 23 January 2017, O'Donnell was named in the Ireland squad for the opening two rounds of the 2017 Six Nations Championship. O'Donnell was also selected in the squad for the 2017 Summer Tour against the United States and Japan. However, an ankle injury ruled O'Donnell out of the tour.