Aberdeen will be playing European football next season after defeating Dundee United 1-0 at Pittodrie.
Adam Rooney’s 27th goal of the season was enough to give the Dons victory but they were forced to play the final 20 minutes with only 10 men after Barry Robson was sent off for violent conduct.
The result ensures the Dons can finish no worse than third place in the Scottish Premiership.
Despite scoring the winner against Kilmarnock last weekend, Cammy Smith dropped out of the starting line-up with experienced midfielder Robson given the nod, while Ash Taylor was preferred to Donervorn Daniels in defence.
An injury-hit Dundee United made three alterations from the side that secured a first league win since January with a 1-0 victory against Hamilton Accies with Jaroslaw Fojut, Calum Butcher and Mario Bilate stepping in for Aidan Connolly, Blair Spittal and Paul Paton.
The match started at a low tempo but it was the Dons who almost drew first blood when Kenny McLean skipped away from Butcher before releasing Jonny Hayes with a perfectly weighted diagonal pass but the Irishman shot straight at Radoslaw Cierzniak.
The Dons had the ball in the net after 29 minutes when McLean headed home Robson’s next corner but referee Bobby Madden had already blown for a foul.
A fairly forgettable first half finally came to life six minutes from half time when the Dons made the breakthrough.
Cierzniak was equal to Mark Reynolds close range effort from a Robson free kick but Rooney was on hand to steer the ball home from close range.
United almost got back on level terms immediately when Chris Erskine fed Bilate but Aberdeen goalkeeper Scott Brown made a smart stop to thwart the United forward.
The Tangerines were forced to make a change immediately after the restart after Bilate suffered a hamstring injury in the opening 15 seconds and was replaced by Robbie Muirhead.
United started the second half on the front foot but were almost caught on the counter-attack with Willo Flood unfortunate to see his long range effort tipped around the post by Cierzniak.
Jackie McNamara’s side were working hard to level the scores with Brown called upon to deny Erskine’s low drive and a curling effort from Muirhead.
A controversial moment was to follow when Robson was shown a straight red card for an apparent elbow on Charlie Telfer.
But the Dons survived the late United pressure to cup Celtic’s lead at the top to five points.