The 26-year-old arrived at the Serie A outfit in November having been released by Real Madrid two months earlier, and made just two appearances during his time at the club.
His last appearance came in the 4-1 defeat to Juventus earlier this month, but errors during the game saw him dropped in favour of Vlada Avramov.
Adan had a contract until the end of the season but will now be looking for a new club, with Cagliari having made the announcement in a short statement on their website on Monday.
The statement read: "Cagliari Calcio announces that it has terminated the contract by mutual agreement with the player Antonio Adan."
His departure adds to speculation that president Massimo Cellino will try to lure Queens Park Rangers goalkeeper Julio Cesar to Sardinia, with the Brazil international keen to play regular football ahead of the World Cup.
