Aitken later went on to play for Newcastle United, joining the club for £500,000 in January 1990. He captained the side in an ultimately unsuccessful attempt to gain promotion from the Second Division. Having been signed by Jim Smith, he was deemed surplus to requirements when Smith was replaced as manager by Ossie Ardiles and returned to Scotland with St Mirren. He did not remain long at St Mirren, signing for Aberdeen for £100,000 to act as player-assistant manager to Willie Miller.