Louw made his debut for as a teenage schoolboy against the British Isles in 1924. His Springbok debut was in 1928 against the visiting All Blacks, when he was selected as lock for the fourth test at the Crusaders Ground in Port Elizabeth. Louw played 18 test matches for the Boks, 13 of which as loosehead prop and scored one try. He also played 31 tour matches in which he scored five tries.