West Brom recorded their first victory in 10 league games thanks to Saido Berahino's late second-half penalty against 10-man Newcastle.
The 20-year-old fired his spot-kick low past Tim Krul after the Magpies keeper had brought down Matej Vydra.
Newcastle looked comfortable until full-back Mathieu Debuchy was sent off for a rash challenge on Claudio Yacob.
The Baggies also went close through Nicolas Anelka and Liam Ridgewell, who both fired wide from close range.
Baggies on top
West Brom have won 47 of the meetings between the two clubs in all competitions, as opposed to Newcastle's 45 victories
Fortunately for the experienced pair, their young team-mate Berahino bailed them out with a cool finish from 12 yards under great pressure.
The England Under-21 forward had come on as substitute at half-time in what was an enforced change by caretaker boss Keith Downing after Billy Jones had been accidentally smacked in the face by his own keeper Ben Foster.
But it could prove be the most inspired change Downing will make during his spell in charge at the Hawthorns. There seems to be no end to the speculation over who will take charge following the sacking of ex-boss Steve Clarke, but if the current man at the helm can follow this win up with another at Southampton, then maybe the club can stop their search.
It was an energy-sapping day at The Hawthorns. Strong winds and driving rain on a soggy pitch were not what the players would have wished for after the busy festive period, and most of the individual performances seemed below par.
There were a few shining lights though, such as West Brom's Morgan Amalfitano. The French midfielder, who is on a season-long loan deal from Marseille, has impressed for the Baggies and was a spritely force down the right.
Two of his assists should have been converted in the opening half. Midfielder Chris Brunt wasted the first chance when he headed an accurate delivery about three feet wide, and in the next attack, Anelka, albeit under pressure, scooped over.
The visitors' best chance in that half, and in the match, fell to Yohan Cabaye, but the France international was unable to find the target from 10 yards.
Berahino took on the good work of Amalfitano after the break by making himself a nuisance on both flanks. He also drove through the heart of the Newcastle defence on one occasion and was unlucky to see his fierce drive blocked by Mike Williamson rather than find the back of the net.
Sending off changed game - Pardew
Newcastle had been defending well up to that point, but their game plan changed just after the half-hour mark when France full-back Debuchy dived in with two feet in a challenge on Yacob. He did not catch the player, but referee Lee Mason deemed it to be a red-card challenge.
The Baggies, with the man-advantage, poured forward - Berahino forcing a low save from Krul before Ridgewell inexplicably missed from four yards.
With four minutes remaining, they finally made the breakthrough when Krul rushed out and clipped substitute Vydra and Berahino stepped up to fire into the keeper's bottom left for his eighth goal of the season.
The win moves the Baggies four points clear of the relegation zone, while the Magpies remain in eighth.
West Brom caretaker boss Keith Downing:
"I am enjoying it. It is easy to say that because I haven't been beaten but for me it was always about supporting the club and that is what I've intended to do, whether win, draw or lose.
"It was important for the club to try to change the momentum and we have done that over the Christmas period."
"The uncertainty can't go on. There has to be a decision eventually.
"They can't just keep making me caretaker in the next month. There has to be a decision from them. January is an important month in the football calendar."
Newcastle manager Alan Pardew:
"I don't think we can have too many complaints.
"I think Mathieu has been our best player this last period, and he is an honest player. He genuinely went for the ball.
"There was no malicious intent, but you can't take off with too feet like that.
"We are going to suffer, and so will he. He will be a big miss for three games, and obviously it affected us today."
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