The forward pounced in the 69th minute to secure the points for Stuart McCall’s side and their first away win of the campaign.
Bradford opened the scoring with a Marek Stech own goal and a Connor Wood strike, with Andy Cook replying with a late consolation after George Lapslie was sent off for two yellow cards.
“The win was great and, with it being our first away victory of the league season, it was pleasing to break that duck,” said Donaldson.
“We played some good football throughout and I thought we definitely deserved it.
“To get an away win so early on in the season will stand us in good stead going forward, because our away form was one of our biggest downfalls last year.
“Scoring three goals away from home is brilliant. It was disappointing to concede near the end of the game, but we will take the result.
“For me to get my first goal of the league season is another key factor for myself. I am definitely happy with it and pleased to have helped the team win.”
City had been lucky when goalkeeper Richard O’Donnell slipped while clearing and gifted the ball to Jordan Bowery who shot straight back at him.
But they took the lead when home keeper Stech dropped Wood’s corner into his own net.
It was 2-0 when Harry Pritchard’s clever flick on Donaldson’s cross set up Wood before Donaldson finished from close range.
Mansfield: Stech, O’Keeffe, Menayese, Rawson (Benning 46), Sweeney, McLaughlin, Maris (Charsley 46), Perch, Lapslie, Maynard (Cook 46), Bowery. Unused substitutes: O’Driscoll, Reid, Sinclair, Stone.
Bradford: O’Donnell, Hosannah, Anthony O’Connor, Richards-Everton, Wood, Mottley-Henry (French 76), Watt, Cooke, Pritchard (Longridge 90), Donaldson (Samuels 86), Novak. Unused substitutes: Hornby, Clarke, Cousin-Dawson, Guthrie.
Referee: P Howard (London).
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