The Latics have now won only one of eight league games under the Scot’s guidance and looked set for their sixth league defeat in that spell right from the first minute.
Donaldson headed in after 67 seconds and made it 2-0 with a tap-in 13 minutes later. James McClean’s superb curling effort reduced the deficit before the break, but the Blues striker’s third just after the hour put the game beyond the Lancashire side.
In-form Birmingham were ahead after barely a minute. Winger David Cotterill delivered a delightful bending cross from deep on the right flank, flighted perfectly for Donaldson to nod home expertly at the far post.
It was 2-0 in the 14th minute and Donaldson was again in the right place at the right time. Andrew Shinnie beat a man to make space inside the box and though his low effort only hit the post, Donaldson pounced to tap in.
The goalscorer nodded wide as the half-hour mark approached then had an effort cleared off the line after he took David Davis’ pass too wide.
Wigan were offering next to nothing going forward, with McClean’s fluffed chance at close range their best work.
Blues were dominating without extending their lead and they paid a price when McClean pulled a goal back in the 36th minute.
The midfielder found space on the right before cutting inside, shifting the ball onto his left foot and bending it in off the far post.
Demarai Gray should have scored City’s third in the 44th minute but after breaking into the box, his tame effort was easily held by Latics goalkeeper Scott Carson.
Wigan were perhaps lucky to have 11 men on the pitch after debutant Liam Ridgewell – subsequently replaced at half-time – appeared to elbow Davis in the face.
Shinnie’s shot from distance in the 54th minute was not far wide before McClean forced a smart save from Darren Randolph at the other end.
Ivan Ramis had two headed chances from corners without finding the target as Wigan tried to muster an equaliser, with the largely poor Shaun Maloney managing a decent effort from distance which Randolph parried away.
But it was 3-1 in the 64th minute as Donaldson claimed his hat-trick, getting a subtle touch on Gray’s header to leave Carson with no chance and Wigan’s comeback hopes over.
The impressive Shinnie was substituted to a standing ovation as Blues saw out the match comfortably to leave Wigan still entrenched in the bottom three.