The Black Cats dominated possession for large spells but couldn't find a breakthrough against a compact Bluebirds defence.
Cardiff then nicked a late winner when defender Mark McGuinness headed home Ryan Wintle’s corner three minutes from time.
Here’s how Phil Smith rated the Sunderland players at the Stadium of Light:
1. Anthony Patterson - 6
Didn’t seem to be a great deal he could do about the goal. Barely tested otherwise, which adds to the frustration of the result. Made one good stop late on as Cardiff broke. 6 Photo: Frank Reid
2. Trai Hume - 5
Made some excellent challenges throughout but looked to tire late on and played some loose passes, one leading to the corner from which Cardiff scored. 5 Photo: Frank Reid
3. Dan Ballard - 6
Had another strong performance, dominating the two strikers over the course of the game. Sunderland will be so frustrated they couldn’t defend their box better from the corner late on, which cost them at least on point. 6 Photo: Frank Reid
4. Luke O’Nien - 6
Looked to be beaten to the ball by McGuinness for the late winner. Had stepped out and swept up well, otherwise. 6 Photo: Frank Reid