Nikki Bull was equal to Jake Reeves early on and left-back Charles Dunne had the Blues’ first attempt, but his 20-yard strike flew over the bar.
Trialist Courtney Harris flashed a shot wide following Stuart Beavon’s clever knock down, however, it was the visitors that should have taken the lead in the 14th minute.
Clayton Donaldson was played through on goal by Reeves, but the striker shot wide from close-range with just Bull to beat.
Farid El Alagui had an effort blocked by the legs of Bull and Lee Angol forced Simon Moore into making a save when he unleashed a powerful strike from just outside the area.
El Alagui somehow shot wide from close-range on the half-hour after Bull had done well to parry Harry Forrester’s piledriver and Grant Basey then cleared off the line as the Bees enjoyed their best spell of pressure.
Brentford finished the half the stronger of the sides and Bull saved from Jonathan Douglas before the midfielder played in Donaldson and he made no mistake from 10 yards to give the visitors the lead in the 37th minute.
The visitors added a second three minutes before the break when Basey, who was put under pressure by a striker, headed past an on-rushing Bull.
Half-time substitute Joel Grant looked lively straight from the restart and was only denied by a fine block.
However, the visitors were still the more dangerous side in attack and Reeves’ free-kick forced Matt Ingram into a save, before the keeper did even better to claw away Douglas’ chip.
Matt Bloomfield had a deflected effort well tipped wide by Moore and Wycombe reduced the deficit in the 58th minute when Brentford defender Dean headed into his own net.
It should have been 3-1 in the 68th minute when Douglas was presented with a tap-in, but he shot into the side-netting.
The Bees didn’t have to wait long for their third though, as two minutes later Shaleum Logan picked out Stuart Dallas with a pin-point cross and he made no mistake.
Sam Wood was denied a goal against his former club by Antoine Gounet, but things got worse for the Blues in the 77th minute when Kevin O’Connor finished from on the goalline after poor defending.
Harris shot wide when well placed a minute from time after a quick break involving Wood and Grant and that was the final chance in what was a disappointing display by the Chairboys.
Wycombe: Bull (Ingram 46), McCoy (Scowen 60), Dunne (Stewart 46), Basey, Doherty (McKenzie 46), Oli (Grant 46), Spring (Bloomfield 46), Kewley-Graham (Lewis 46), Harris, Angol (Wood 46), Beavon (Logan 46).
Brentford: Moore (Gounet 70), Logan, Vignal (Redwood), Craig (Oyeleke 78), Dean (Legge 64), Saunders (Dallas), Reeves (Onovwigu 72), Douglas, Forrester (Mawson 78), Donaldson (Weston 60), El Alagui (O'Connor 60).