In 1944 the Labour Party split and Pattison became a member of the new political movement, the National Labour Party. The split was healed when new party merged with the Labour Party in 1950.
When the Carlow–Kilkenny constituency was split at the 1937 general election, Pattison was re-elected in the new 3-seat Kilkenny constituency. He retained that seat through three more general elections, and was returned again for Carlow–Kilkenny when the constituency was recreated for the 1948 general election. However, he lost his Dáil seat in the 1951 general election to the former Fianna Fáil TD Francis Humphreys, but regained it at the 1954 general election. He was defeated again at the 1957 general election, again by a Fianna Fáil candidate, and decided to retire from national politics.