Neil Warnock's men had suffered four straight defeats prior to Saturday's result, but kept Black Cats boss Chris Coleman without a win in Wales to move one point above third-placed Derby County.
Cardiff shared the best of the opening 10 minutes, as Sean Morrison's header from Joe Ralls's free kick was easily saved by Robbin Ruiter, before Ralls's corner bounced dangerously through the Black Cats' box before being cleared.
Ralls had the game's first decent chance when Billy Jones's clearance was met on the half-volley by the Englishman before Ruiter tipped wide.
Cardiff had more opportunities to take the lead in the first half through Junior Hoilett, who had two free kicks that were both steered just wide.
The Bluebirds continued to press before the half-time whistle but were unable to find a breakthrough.
Warnock's men, however, began the second period how they ended the first, and were ahead on 46 minutes when Callum Paterson rose above Jones and headed past Ruiter.
Sunderland's afternoon got worse when Didier N'Dong, who returned to the squad this weekend, was shown a straight red card for a challenge on Hoilett.
The hosts capitalised on their numerical advantage from a Black Cats corner, from which Hoilett raced away and squared to feed Ralls, whose first-time effort beat Ruiter.
From then on, Sunderland were poor as Paterson added his side's third and the visitors failed to find a response.
CARDIFF: Etheridge; Richards, Ecuele Manga, Morrison, Bamba; Bennett, Mendez-Laing (Wildschut 59'), Paterson, Ralls; Hoilett (Feeney 81'); Zohore (Pilkington 82')
SUNDERLAND: Ruiter; Jones, Clarke-Salter, Browning, O'Shea, Oviedo; Honeyman, Wilson (Cattermole 45'), Ndong, Gooch (Asoro 60'); Maja (McManaman 78')