Miguel Almiron tucked away his first Premier League goal of the season inside the opening 20 seconds to give his side the dream start.
West Brom levelled six minutes into the second half through a lovely Darnell Furlong after the hosts momentarily switched off.
United weren't finished then though when substitute Dwight Gayle - making his first appearance since the final day of last season where he scored against Liverpool - scored the winner.
Fast start
It was an unusual sight to see a Newcastle side who have lacked in attacking highlights so far this season to race out of the blocks as quick as they did.
Joelinton picked up the ball in a promising area but still had a lot to do when he found an on-running Almiron who punished the Baggies' sloppy start.
It was another vastly encouraging piece of play from the Brazilian in his more suited just off the main striker.
From then on, however, Steve Bruce's side struggled to kick on and grab the game by the scruff of the neck, and their opposition gradually came into the contest.
Momentum switch
In credit to the visitors, many may have expected another collapse like we saw in their defeat to Crystal Palace six days ago, but they didn't allow that to happen.
Joelinton had a decent chance to make it two on 16 minutes when he worked his way in on goal from an acute angle but saw his shot blocked by Sam Johnstone.
Two minutes before the half-time whistle Slaven Bilic saw his side come close when the in-form Chelsea loanee Sam Gallagher fired wide from a promising position inside the area.
At that point it may have appeared to be one of those days for the Baggies, but that all changed on 50 minutes when a cross from the left-hand side wasn't dealt.
Furlong beat Jamal Lewis to the ball before finishing first time leaving Karl Darlow with no chance.
It capped a difficult day for the full-back, who was hooked shortly after for the eventual winner Gayle.
Super sub Gayle has still got it
It may have been a brave shout from Bruce to bring on a forward who hasn't played a single minute since recovering from a knee ligament injury.
Project Restart was a productive period for United's most long serving striker who scored four goals during that time, and he continued where he left off today.
A fantastic in-swinging cross from fellow sub Jacob Murphy picked out Gayle who's powerful header was too good for Johnston.
It seemed cruel on West Brom, and there were some positives to take after going one down so early, but perhaps a lack of concentration late became their undoing.
Bruce had to endure over six minutes of added time at the end but you sensed the Baggies had ran out of steam, on a day where it might have been different.