Ex-United defender Bruce got his first win over his old club at the 23rd time of asking as the Tyneside outfit moved out of the relegation zone, while the Red Devils slipped to within two points of the bottom three.
Ole Gunnar Solskjaer’s side have taken nine points from their first eight games; their lowest tally at this point since the 1989-90 season.
Bruce, in his 400th Premier League game as a manager, made five changes to his Magpies side from the 5-0 loss to Leicester City and watched his team make a bright start, Allan Saint-Maximin causing issues and firing narrowly early on.
Matt Longstaff, making his first Premier League start, then went close to opening the scoring when his long range drive clipped the top of the crossbar.
Fabian Schar saw a glancing header drift over the top of the woodwork from a Sean Longstaff corner as Manchester United struggled to get going in the first half.
Miguel Almiron was then denied his first goal in black and white by a great block from Harry Maguire as Newcastle kept up the pressure.
However, it was the Red Devils who should have gone in at the break ahead, Maguire missing from six yards out with a header with the goal at his mercy just before the interval.
Newcastle introduced Andy Carroll just before the hour mark following another disappointing showing from Joelinton in the hope of opening up a tight game.
The 30-year-old striker nearly made a breakthrough when sending a header over the bar as both sides continued to find it tough to fashion chances.
With the Magpies tiring, United start to open up the home side, Schar having to make a great clearance to stop Marcus Rashford tapping home midway through the half.
With United pushing forward, Newcastle caught the Red Devils on the counter on 72 minutes, another strong run from Saint-Maximin setting up the chance for Matt Longstaff, who drilled his shot past David de Gea to notch on his league debut.
Substitute Marcos Rojo sent a header over from an Ashley Young freekick as United went in search of an equaliser.