Second-half strikes from Alejandro Garnacho and Rasmus Hojlund helped the Red Devils claim three much-needed points, ending their five-game winless run in all competitions and somewhat easing the pressure that has mounted on Erik ten Hag's shoulders in recent weeks.
Brentford were unable to continue their ridiculous run of scoring early openers, but they made the brighter start to proceedings at Old Trafford, boasting almost 70% possession in the first 20 minutes.
Man United responded well, though, and came close to scoring the opener when Lisandro Martinez's header from a corner was initially fumbled by Mark Flekken, and the ball almost cross the line after hitting Hojlund's back, but the Bees goalkeeper managed to claws it away.
Andre Onana was called into action to prevent a beautifully-struck curler from Brentford captain Christian Norgaard from creeping into the far corner, but he was unable to keep out the visitors' opener in the fifth minute of first-half stoppage time.
Just seconds after Matthijs de Ligt was told by referee Sam Barrott to leave the pitch and have his head wound treated, Brentford took the lead courtesy of Ethan Pinnock's bullet header from Mikkel Damsgaard's corner.
Man United were left enraged as they headed into the interval, but they needed just 89 seconds to restore parity in the second half, with Marcus Rashford's delightful cross from the edge of the area smacked home at the far post by Alejandro Garnacho.
The Red Devils were pummelling the Bees and deservedly took the lead just after the hour mark when Rasmus Hojlund delicately chipped the ball over Flekken after receiving a fancy flick in behind from Bruno Fernandes.
Brentford were unable to respond in the closing stages and Man United held on for just their third Premier League victory of the season, moving them up to 10th in the table, while Thomas Frank's side have slipped to 12th after eight matches.
MAN UNITED VS. BRENTFORD HIGHLIGHTS
Ethan Pinnock goal vs. Man United (45 + 5 min, Man United 0-1 Brentford)
With De Ligt forced to leave the pitch to have his head wound treated, Brentford capitalise at a corner from the left, with an unmarked Ethan Pinnock bursting towards the front post to thump Mikkel Damsgaard's cross into the back of the net.
De Ligt, Ten Hag and his assistant Ruud van Nistelrooy, who were all furious with the referee's decision to send De Ligt away for treatment while defending a corner, were all booked for their protests, and boos rang around Old Trafford as the players and officials headed down the tunnel at the interval.
Alejandro Garnacho goal vs. Brentford (47 min, Man United 1-1 Brentford)
Man United burst out of the blocks in the second half and restored parity just 89 seconds after the restart when Marcu Rashford curled a magnificent cross from deep on the right towards the back post, where Alejandro Garnacho fired a first-time side-footed shot beyond Flekken at his near post.
Rasmus Hojlund goal vs. Brentford (62 min, Man United 2-1 Brentford)
Christian Eriksen pounced on a poor clearance from Nathan Collins and played a pass to Bruno Fernandes, whose fancy first-time flick on the edge of the area allowed Rasmus Hojlund to run in behind and dink a delicate, composed finish over Flekken and into the far corner.
MAN OF THE MATCH - ALEJANDRO GARNACHO
Garnacho frustratingly lacked a cutting edge in the final third during the first half, but he improved immensely after the break and was hugely influential in helping Man United turn the contest on its head.
The Argentine's well-taken goal goal less than two minutes into the second half set the tone for the Red Devils in the second half, and his infectious energy and willingness to work for the team at both ends of the pitch was a joy to watch for the Old Trafford faithful.
MAN UNITED VS. BRENTFORD MATCH STATS
Possession: Man United 51%-49% Brentford
Shots: Man United 23-8 Brentford
Shots on target: Man United 11-2 Brentford
Corners: Man United 9-2 Brentford
Fouls: Man United 4-5 Brentford
BEST STATS
WHAT NEXT?
Man United will now turn their attention back to the Europa League and will prepare for a trip to Turkey on Thursday when they do battle with Jose Mourinho's Fenerbahce.
As for Brentford, they have a whole week to prepare for their next Premier League fixture against newly-promoted Ipswich Town at the Gtech Community Stadium next Saturday.