Manchester United made a winning start to life under interim boss Ralf Rangnick thanks to Fred's 77th-minute winner.
A more energetic United display looked like going unrewarded against a dogged Crystal Palace outfit until Fred struck first-time from Mason Greenwood's lay-off to send a superb 20-yard effort curling over Vicente Guaita and into the top corner.
It was only Fred's second goal of the season - and the first time since the middle of September that United have recorded back-to-back league wins.
Until the Brazilian's effort, Rangnick's side created numerous decent chances, without really looking as though they were going to score and Guaita would probably have saved an Alex Telles free-kick that skimmed the bar had it been on target.