Like his son John Aston Jr., Prestwich-born Aston came through the Manchester United youth system and turned professional in December 1939. His debut for the club came on almost seven years later, on 18 September 1946, against Chelsea. Aston was a strong, tough-tackling left-back who also played as a centre forward for his club on occasion. He won 17 England caps between 1948 and 1950, all at left-back, and featured in the 1950 FIFA World Cup. He played in the 1948 FA Cup Final triumph over Blackpool at Wembley Stadium. He left the club in 1954 after scoring 30 goals in 284 appearances.