A late Ivan Toney goal condemned Albion to a 1-0 defeat in their penultimate pre-season friendly at the Amex on Tuesday.
Graham Potter made 11 changes to the team that started last Saturday's 2-1 win at Reading.
The afternoon saw first Amex run outs for Matt Clarke, Jan Paul van Hecke, Julio Enciso, Kaoru Mitoma, Kacper Kozlowski and Deniz Undav.
The Bees gave Ben Mee his debut, the defender having completed his move from Burnley last week.
Some quality deliveries into the box from Enciso are hopefully a taste of what’s to come from the Paraguayan. Matt Clarke nodded home at the back post from the 18-year-old’s whipped free-kick from the right after eight minutes, but the Albion defender was adjudged to be offside.
Undav was denied by goalkeeper David Raya from 12 yards, before van Hecke’s header was cleared off the line following Enciso’s corner.
Shandon Baptiste forced Jason Steele into his first save of the afternoon with a low drive that the keeper palmed behind for a corner, before Undav played in Neal Maupay who smacked the inside of the post before Mitoma’s follow up was smartly tipped wide by Raya.
Van Hecke got on the end of Clarke's nod towards goal early in the second half but couldn't direct it past Reya then Mitoma's dart into the box and subsequent pull-back for Undav was blocked before the German volleyed the loose ball over, as Albion pressed for the goal their pressure deserved.
Kacper Kozlowski's corner was flicked on by Clarke and Florin Andone couldn't poke home after some pinball in the Brentford box.
Albion had looked the team likelier to break the deadlock but instead Brentford took the lead with 12 minutes to go. Kjell Scherpen's pass out was intercepted by Halil Dervisoglu, who set Ivan Toney up for an easy finish into an empty net.
Albion now look forward to the final game of pre-season, as they welcome La Liga outfit Espanyol to the Amex on Saturday.
Albion line-up: Steele (Scherpen 60), Duffy, Clarke, van Hecke, Enciso (Karbownik 60), Mitoma (Moran 69), Alzate, Sarmiento (Zeqiri 60), Lallana (Kozlowski 60), Undav (Andone 69), Maupay.
Unused subs: Jenks, Spong, Turns, Beadle.