Walker earned a total of 21 caps, during which he scored 9 goals. He scored in five consecutive games from April to December 1938. All but one of these caps were obtained before the age of 25 and had the Second World War not intervened, he would have garnered considerably more. If the ten caps he earned in Wartime Internationals were to count, he would have become the most capped Scottish player. He also won five Scottish League XI caps, scoring two goals.