A second-half blunder from Costel Pantilimon made it a losing start to Sam Allardyce's Sunderland reign as Saido Berahino scored the only goal of the game in a 1-0 Premier League win for West Brom.
Allardyce took charge at Sunderland last week after Dick Advocaat left the club with the Wearsiders having claimed just three points from their opening eight games of the campaign.
Sunderland's porous defence appeared more solid in the clash at The Hawthorns on Saturday, but their hopes of a maiden league win were ended by a handling error from goalkeeper Pantilimon.
The Romania international failed to control a ball from West Brom midfielder Chris Brunt in the 54th minute, presenting Berahino with the simple task of tapping into an empty net.
From there Sunderland never looked like mounting a comeback as West Brom dictated the game and pressed for a second to end the contest.
Despite failing to double their lead, West Brom were rarely troubled in the second half and did enough to avoid a third straight defeat and condemn Sunderland to a sixth league loss of what has so far been a miserable campaign.
Sunderland had the better of the opening exchanges and only the fine reflexes of Boaz Myhill prevented the visitors from taking the lead, the West Brom goalkeeper turning over Billy Jones' diving header from point-blank range in the 11th minute
West Brom found chances hard to come by and their best effort came from former Sunderland winger Stephane Sessegnon - in for the injured James Morrison - who curled wide from the edge of the area 10 minutes later.
Allardyce, whose side went into the game having shipped 18 goals in the league, will have been impressed by Sunderland's ability to frustrate West Brom, with the West Midlands club reduced to shots from distance despite enjoying much of the possession.
But their hard work was undone nine minutes after the restart courtesy of a dreadful error from Pantilimon.
The former Manchester City keeper fumbled Brunt's left-wing cross under pressure from Berahino, who capitalised by back-heeling the ball towards goal and then prodding home at the far post.
Brunt came closing to providing the assist for the second goal with another delivery from the left, but Salomon Rondon could only fire the ball over from close range.
West Brom were perhaps fortunate not to concede a late penalty for an ill-advised Sessegnon challenge on Jones, but that was the only real scare for Tony Pulis' men in the second half as they held on with relative ease.
