Over the summer break, Brentford brought in right back Henrik Dalsgaard from Zulte Waregem for an undisclosed fee and goalkeeper Luke Daniels from Scunthorpe United on a free transfer.

[7] Goalkeeper Jack Bonham signed a new one-year contract extension and moved to Carlisle United on loan until January.

[10][11] On 7 July, South African midfielder Kamohelo Mokotjo signed for an undisclosed fee from Dutch side FC Twente.

[16] Following their return to England, Brentford signed EFL Young Player of the Year Ollie Watkins from Exeter City for a reported £1.8 million fee.

[21] The unbeaten pre-season campaign continued at MK Dons where Maupay, Watkins and Jozefzoon all scored in a 3–2 win against the League One side.

After John Egan's header, two stunning strikes from Andreas Bouchalakis and Daryl Murphy's tap in left the Bees trailing 3–1 midway through the second-half.

Andreas Bjelland gave some hope for Brentford as his header was adjudged to have crossed the line by goal-line technology, a first for Griffin Park.

Despite conceding an early Josh Brownhill goal, Brentford rallied in the second half and took the lead through Watkins and Maupay and would have been further in front had it not been for an inspired performance from opposing goalkeeper Frank Fielding.

Eight minutes into added time due to an injury to Josh McEachran, Bobby Reid pounced and denied Brentford's first league win of the season.

[33] The Bees' poor run of results continued at Ipswich Town where, despite a dominant first half, Martyn Waghorn and Joe Garner's goals sealed a 2–0 win for the home side, leaving Brentford bottom of the league table.

[34] In the second round of the League Cup, Brentford beat local rivals Queens Park Rangers 4–1 in a West London derby.

Yennaris scored early with a volley but Gary Hooper netted on the brink of half-time and Ross Wallace completed the comeback from Jordan Rhodes' pull-back.

Clarke rifled in from a tight angle after good play between himself and Maupay but Liam Kelly equalised with a penalty after Rico Henry fouled Tyler Blackett as the game ended 1–1.

Vrancic then curled in a free kick in the second half and Josh Murphy chipped over the oncoming Daniels to give the Canaries a three-goal advantage.

Despite completely dominating, Brentford could not break down the Derby defence and found themselves behind to Joe Ledley's debut goal for the Rams.

Despite scoring two goals, courtesy of Barbet's header and Watkins' finish, Middlesbrough came back from behind twice through Martin Braithwaite and Fabio to secure a 2–2 result.