The Blades returned to Championship football with a deserved victory.
Skipper Billy Sharp scored the all-important goal with a first half header in a game that saw 'goals' ruled out and the woodwork struck on numerous occasions.
Boss Wilder's first Championship selection included three new starters. Blackman, Stevens and Stearman made their competitive Lane bow, with Lundstram among the substitutes.
The Blades won a free-kick in a dangerous position and a corner inside two minutes - a frantic opening was entertaining for the bumper crowd.
O'Connell was forced to concede a corner to cut out Dalsgaard's cross and Jota's shot was tipped over by Blackman after Fleck surrendered possession as the visitors looked a threat. United's best early chance saw Stevens hold up a cross but Clarke could not get enough on his header.
Jota shot wide after Vibe beat the offside trap but as the half hour mark approached United looked to force Brentford back and went mightily close on 25 minutes. The ball broke to Stevens 25 yards out and his shot deflected off a defender onto a post and dropped, frustratingly, straight into goalkeeper Bentley's grasp.
A spell of pressure saw Basham come close to connecting with a header at the back post, Coutts have a shot blocked and a penalty appeal, but the opening goal was not too far away.
On 39 minutes, a corner from the left was recycled at the back post by Clarke, who clipped in a cross and SHARP found space in the box to head home, despite Bentley getting a hand to the ball.
Sharp's celebrated but was soon holding his head after a clash with Egan - both needed treatment - whilst the remaining first half minutes saw the Blades stay on top.
Like the first half, the start of the second was hectic. Within 40 seconds of the restart, Clarke's persistence saw him get the better of Henry but after the subsequent cross Sharp's header saved by Bentley.
Jota shot at Blackman from distance but United remained the dominant force and had two goals ruled out for offside in the space of two minutes! Firstly, after Stearman had hooked the ball back into the box, Clarke bundled home but the linesman was maybe too keen to put up his flag. Soon after, following a foul on Carruthers, a clever free-kick saw Fleck curl against a post and Sharp tucked home the rebound but again the flag was raised.
Fleck hit a right foot shot just wide but Brentford emphasised that they were a threat with a triple chance just after the hour. Jota's long range shot was batted away by Blackman, Yennaris headed the rebound against the crossbar and Vibe headed the second rebound over from a matter of yards.
On 68 minutes, O'Connell produced a great block after a Watkins pass had put Vibe in and Wilder's first change saw Lundstram take over from Carruthers.
As the game reached the final 20 minutes, both teams were visibly tiring. Brentford used their final substitute and Lavery took over from Sharp.
A fantastic pass from Woods put the fresh legs of Maupay in the clear on 81 minutes but the substitute was denied by a tremendous save by Blackman.
Brentford were now forcing the issue and United were defending doggedly. On 88 minutes Maupay curled over after linking up with Watkins.
The visitors were patient but the Blades protected Blackman well and three minutes of added time saw the likes of Basham, Stearman and O'Connell all involved before the three points were confirmed.
Blades: Blackman, Stevens, Fleck, O'Connell, Basham, Clarke, Sharp (Lavery 78), Coutts, Freeman, Stearman, Carruthers (Lundstram 70).
Unused: Wright, Duffy, Lafferty, Eastwood, Brooks.
Brentford: Bentley, Henry, Bjelland, Jozefzoon (Watkins 59), McEachran (Maupay 78), Mokotjo (Yennaris 59), Egan, Woods, Vibe, Dalsgaard, Jota.
Unused: Colin, Sawyers, Daniels, Barbet.