Aston Jr joined the Manchester United ground staff as an apprentice in July 1962. He signed as a trainee in July 1963 and in July 1964 he signed as a professional.

He made his League debut on 12 April 1965. In 1967 Aston won a League Championship medal, playing in 34 (3) games and scoring 10 goals.

Aston is best remembered for his performance in the 1968 European Cup Final, when he had the game of his life when United lifted the European Cup.

In July 1972 John Aston moved to Luton Town for a fee of £30,000 after a broken leg had all but ended his playing career at Old Trafford.

John Aston Snr (1952) and John Aston Jnr (1967) are the only known father and son to win League Championship medals with the same club.