The 22-year-old defender has signed a pre-contract deal after being told last week that he would not be offered a new contract at Pittodrie.
The Irishman made almost 60 appearances for the Dons but only two this season and was loaned to Falkirk for several months.
The Galway-born defender has been at Aberdeen since 2009 and has had loans spells in that time at Forfar Athletic and Falkirk. He has also represented Ireland at Under-21 level.
Aberdeen Mad has always been a fan of Joe's committment and attitude and is sad to see him go, but wishes him all the best in the future – except against the Dons.
Shaughnessy had this to say on Twitter:
... pic.twitter.com/0GCiXunsRb
— Joe Shaughnessy (@Joe_shaughs) May 20, 2015