Aaron Wilbraham's first league goal of the season proved decisive as MK Dons leapfrogged Exeter into seventh place in League One with a 1-0 win.
Wilbraham marked his return from a three-week injury lay-off with a cool 53rd-minute winner to condemn the Grecians to their third straight defeat on the road.
Exeter dominated the first half but Ryan Harley fired straight at keeper David Martin following a neat turn on the edge of the box before John O'Flynn had a goal ruled out for offside in the 37th minute.
For the Dons, Sam Baldock lobbed straight at keeper Paul Jones and Luke Chadwick sliced wide from 22 yards. But the Dons improved after the break and Wilbraham put them ahead eight minutes after the restart when he controlled substitute Mark Carrington's chip over the defence and neatly slotted the ball past Jones.
Jones denied both Baldock and substitute Jermaine Easter one-on-one as the Dons pressed for a second goal.
Exeter piled forward late on in search of an equaliser but Martin saved well from Ryan Harley and twice denied O'Flynn as the Dons hung on for the three points.