By James Pearson
Last Updated: 01/01/70 1:00am
The 25-year-old defender, who was recently included in Scotland B's recent clash against Turkey, had been hoping to remain with The Dons next term.
Manager Steve Paterson did offer seven first-team players new deals on Thursday, but opted against retaining McAllister.
The Glasgow-born full back had been a regular under former boss Ebbe Skovdahl, making 26 league starts this term, but was not first choice under Paterson.
"Getting involved with the Scotland set-up was a tremendous boost and this news was the last think I wanted to hear," said a disappointed McAllister.
"It is a real shock to be told you have no future at the club, but there was a hint of what was going on as they had refused to discuss things with my agent.
"To be honest I would have preferred to at least have had the option of staying at Aberdeen. But hopefully I can get another club sorted out."