A 10th-minute red card for Josh Dasilva following a horror tackle of Matt Targett swung the game in Eddie Howe side’s favour.
Joelinton headed the Magpies in front on 33 minutes before Joe Willock extended the lead not long later.
While the Bees, boosted by a return to football for Christian Eriksen, pushed in the second-half but United held out fairly comfortably.
The three points lifts Newcastle above their hosts into 14th, four points above the Premier League relegation zone.
Here’s our writer Jordan Cronin’s player ratings from the victory at the Brentford Community Stadium.
1. Martin Dubravka - 7
Another quiet afternoon for the Slovakian, which is a testament to how vastly improved Newcastle are as a defensive unit. First notable save came during injury time when he kept out Vitaly Janelt’s effort. Photo: Alex Burstow
2. Emil Krafth - 7
Credit to Krafth, who supporters are a constant critic of. With Javier Manquillo back on the bench, the Sweden international gave Howe no reason to drop the Sweden international ahead of hosting Brighton and Hove Albion next Saturday. Photo: Warren Little
3. Fabian Schar - 8
What an assist for Willock’s goal! Schar did brilliantly to bring a long clearance under control before setting up the Magpies’ second goal of the afternoon. Could have found the scoresheet himself but wasted a free header just after half-time. Photo: Stu Forster
4. Dan Burn - 7
Burn endured a nevry start to the game with Bryan Mbeumo’s pace often getting the better of the Blyth-born defender. However, as Brentford were reduced to 10 men, and United jumped ahead on the scoreline, Burn eased into it. Photo: George Wood