He won his first cap for Wales against Ireland in 1951, playing opposite his own hero Jack Kyle. He was part of the Grand Slam-winning Welsh side of 1952. The following year he inspired both Cardiff and Wales to historic victories over the touring All Blacks. In 1956, following his success on the 1955 British Lions tour to South Africa, he was made captain of Wales. During that tour, in which the Test series was drawn 2–2, Morgan distinguished himself for his marshalling of a talented Lions backline that included Jeff Butterfield and Arthur Smith in the centre, with Cecil Pedlow and Tony O'Reilly on the wings. Morgan's try in the first Test at Ellis Park, in front of a then world-record crowd of 100,000, helped secure a sensational 23–22 victory at the end of a match that some still consider the most exciting ever played.