The Black Cats fell behind in the 13th minute when Luke Cundle’s effort deflected off Luke O’Nien and past goalkeeper Anthony Patterson.
It was a tough first half for Tony Mowbray’s side as the hosts dominated possession and doubled their lead through Harry Darling on the stroke of half-time.
Sunderland pulled a goal back through Jack Clarke at the start of the second half but couldn’t salvage a point.
Our Sunderland writer Phil Smith has dished out his player ratings from the Swansea.com Stadium:
5. Aji Alese - 7
Another hugely tenacious performance from the youngster, particularly in the second half when he defended well and broke forward with impressive athleticism at the end of a demanding week. 7 Photo: Frank Reid
6. Corry Evans - 5
Looked off the pace in the first half but better in the second, picking up good positions to help his side build attacks. 5 Photo: Stu Forster
7. Dan Neil - 5
Stepped onto every second ball in the second half and knitted play together well, a complete transformation from the opening exchanges where Swansea played through the visitors at will. 5 Photo: Martin Swinney
8. Alex Pritchard - 5
Moved back into the false nine role but wasn’t able to see any of the ball in dangerous areas. More of an influence after the break when Sunderland saw more of the ball in Swansea’s half. 5 Photo: Frank Reid