Later Parliamentary career
After Labour's victory in the general election of 1945, Lawson won a seat in Clement Attlee's Cabinet, becoming Secretary of State of War. Within this role he travelled far and wide, speaking at military functions and public meetings. Lawson oversaw planning for post-war operations, and served as a key ally for Clement Atlee, particularly during conflicts with other Parliamentarians. However, despite his significant position, Lawson began to suffer severe health problems. He retired from the front bench in October 1946, becoming vice-president of the National Parks Commission.
House of Lords
In 1949, on Clement Attlee's recommendation, Jack Lawson was appointed as Lord Lieutenant of Durham and in March 1950 he joined the House of Lords, taking the title Baron Lawson of Beamish. He did attend the House of Lords but did not take a front-bench position. Within his time in the House of Lords he continued to provide support to the Labour Party, particularly during the 1950s. Lawson died in 1965, at the age of eighty-three.