Salmon Rondon scored the winner in the second half for the Baggies after he smashed the ball home past David de Gea, but United's hope of a win were ended when Juan Mata was sent off for two bookable offences inside half an hour.
United reduced to 10
United began the game on the front foot and looked confident after the run of consecutive wins, passing the ball around well. Yet, it was all in front of the West Brom defence. Anthony Martial had United's first shot of the game when he tested Ben Foster from outside the box.
However, the United players continued to huff and puff without doing much with the ball and the game started to get scrappy - which contributed to Mata receiving a red card for two yellows in the space of five minutes. The dismissal meant that United were up against it for the remaining hour.
West Brom almost got the first goal of the game when Craig Dawson shot from 40 yards and it dipped just wide of de Gea's goal. The crowd started to get behind the hosts, and they were responding to them.
The rest of the half saw a couple of half-chances for the home side, but Chris Smalling - back from injury - stopped a certain goal from Saido Berahino with a superb block.
The first half was a very scrappy contest between the two sides with the quality seriously lacking in the game. United started the game stronger, but after the red card, they couldn't really get hold of the ball and had their backs against the wall.
Good start to the second period for the visitors
The second half began with the United players looking determined to go for the win. Martial created a half chance for Marcus Rashford when he took on three West Brom defenders and laid the ball back to his teammate at the edge of the box, but the striker's shot was deflected just wide.
The visitors continued to play with confidence as Jesse Lingard shot from a long way out - his effort going just over the bar. On a few occasions at the start of the half, the United players started playing it long to Martial with the striker giving the team a real threat on the break.
Rondon scores the winner for the Baggies
However, the home side responded to United's pressure by scoring the opening goal when a good move saw Rondon smash the ball past de Gea. The cross for the striker was provided perfectly by left back Sebastian Pocognoli, and the visitors suddenly had it all to do with 10 men.
United just couldn't get going after West Brom's goal, with the home side stopping any attacks that were going against them. Memphis Depay came on to try and change this and instantly won a free-kick in a dangerous position. He took it himself, putting a good ball into the area, but no one was there to head home.
The game ended in defeat for United, Rondon's goal midway through the second half the winner. The defeat put an end to United's mini-revival of four consecutive wins and put their charge for a top-four place on hold, for the time being.