Zoltan Gera's brilliant strike, a dreadful blunder by Sunderland goalkeeper Simon Mignolet, which gifted Shane Long a goal, Romelu Lukaku's penalty and Marc-Antoine Fortune's late finish gave Steve Clarke's side the points despite Craig Gardner's free-kick and Stephane Sessegnon's late tap-in having given the home fans something to cheer.
The win pushed West Brom above Chelsea, who host Manchester City in Rafa Benitez's first game in interim charge on Sunday, on to a total of 26 points from 13 games in what is emerging as an unexpectedly successful campaign.
In contrast, defeat for Sunderland added to the pressure on Martin O'Neill, which had only been temporarily lifted with last weekend's win at Fulham, and the Black Cats have now still won just one home game this season to leave them languishing close to the relegation zone.
The match's first real talking point came in the 20th minute when relieved Sunderland defender John O'Shea thought he had been shown a second yellow for a challenge on Long only to realise his Republic of Ireland team-mate had been harshly booked for diving.
Boaz Myhill was then fortunate not to be punished when the West Brom goalkeeper only palmed a header from Sessegnon, clearly full of confidence after his spectacular goal at Fulham, back into the danger zone.
But, in the 30th minute, Sunderland paid the price for their missed chances as Gera gave West Brom the lead by curling an excellent, left-footed, 25-yard effort past Mignolet, who could only brush his fingertips against the ball.
Mignolet and Sunderland's problems deepened one minute before half-time when the goalkeeper made an embarrassing hash of dealing with Chris Brunt's harmless, over-hit through-ball, allowing Long to pounce and walk the ball into the open net.
O'Neill, who had lost captain Lee Cattermole to injury in the first half, made another change at half-time and sent on James McClean in place of O'Shea, with Phil Bardsley moving to centre-back and Sebastian Larsson shifting to right-back.
But West Brom continued to look a threat on the counter-attack and Mignolet had to partly atone for his earlier blunder by saving a one-on-one with Long when rushing off his line to block the striker.
Sunderland, though, were back in the game in the 73rd minute when Gardner, who returned from suspension as a replacement for Cattermole, hit a free-kick and saw it deflect off the wall to beat Myhill.
The strike lifted Sunderland's spirits but it was short-lived as substitute Lukaku's 81st minute penalty, after Liam Ridgewell had gone down somewhat softly under a challenge from Adam Johnson, and Fortune's injury-time goal sandwiched Sessegnon's close-range finish at a corner.
|Sunderland||Team Statistics||West Bromwich Albion|
|0||1st Half Goals||2|
|10||Shots on Target||6|
|7||Shots off Target||6|
|48.6||1st Half Poss.||51.4|
|47||2nd Half Poss.||53|