“He is now at an important stage of his career where he wants the opportunity to play every week and unfortunately, we are not in a position to offer him that at the moment.
“I’ve no doubt Niall’s determination will prove him a success at his next Club, and he goes with our very best wishes.”
In total the former Dungannon Swifts man made 358 appearances, of which 299 were starts. He also scored 87 goals which means the 34-year-old is in 15th position on the all-time Aberdeen appearance list and 19th in the club's goalscoring charts.
He's expected to go straight into the Dundee squad for Wednesday’s match with St. Johnstone.