A first-half strike from Demba Ba condemned Albion boss Steve Clarke to defeat on his return to Stamford Bridge.
Ba turned home a David Luiz knock-down to punish the Baggies for a flat display in the opening 45 minutes.
Clarke’s men improved after half-time and fought hard late on, but they could not find an equaliser as the hosts triumphed despite more protests and banners from Blues fans directed at interim manager Rafa Benitez.
Chelsea made a bright start and Baggies keeper Ben Foster, being watched from the stands by England manager Roy Hodgson, had to make a brilliant save early on.
Oscar turned a fantastic Ramires cross towards goal from eight yards out but Foster made an instinctive point-blank block.
But on seven minutes Albion tested Petr Cech in the Chelsea goal.
Steven Reid hammered a free-kick from 30 yards and Cech had to push it over the crossbar.
The home side continues to make the running and they had another great chance in the 16th minutes when Oscar got in front of Steven Reid to meet a cross by Cesar Azpilicueta.
The Brazilian had a free header but he placed it straight at Foster.
Foster was called upon again when he dived high to his right to turn a deflected David Luiz free-kick behind for a corner.
But the Baggies keeper was partly at fault for the opening goal, which came from the resulting corner.
The flag-kick was taken short and found its way to Oscar, who delivered a far-post cross that caught Foster in no man’s land.
David Luiz was free to head the ball across goal and Ba was unmarked as he turned it in.
Chelsea were well on top but the Baggies had a rare shot at goal just before half-time.
Shane Long nodded down a diagonal ball but James Morrison sent his effort well over.
Chelsea had the ball in the net early in the second half but Frank Lampard’s ‘goal’ was ruled out for offside against provider Juan Mata.
And the Blues were screaming for a penalty when Eden Hazard tangled with Jonas Olsson and went down in the box.
But referee Kevin Friend waved away the appeal with replays showing minimal contact.
Foster was twice called upon to deny Oscar in the second period, first with a brave block and then with a reaction save low to his right.
But Albion fought hard late on and Cech had to make an excellent stop to prevent an own-goal when Azpilicueta diverted Morrison’s corner towards his own goal.
By Steve Madeley