Waddell first represented Scotland in the opening game of the 1924 Five Nations Championship, played against France. Although Scotland lost, Waddell scored his first international in the game with a dropped goal, and was reselected for the rest of the tournament. During the 1924 Championship, Waddell scored a try in a humiliating win over Wales, and a pair of tries in a home victory over Ireland. Although the tournament ended in a poor loss to the eventual champions, England, it turned into a good year for Waddell, with an invitation to tour with the Barbarians immediately after the England game; and then selected to represent the British Isles on their tour of South Africa.