On 25 June 2015, Barbet moved to England to sign a four-year contract with Championship club Brentford for an undisclosed fee. He made his debut with a start in a 4–0 League Cup first round drubbing at the hands of Oxford United on 11 August and possibly put through his own net for the Us' second goal, which was credited to Danny Hylton. With Jack O'Connell largely preferred as third-choice centre back behind Harlee Dean and James Tarkowski, Barbet spent long periods in and out of the matchday squad through to the end of 2015. The unavailability of Tarkowski saw Barbet make his first appearance in over four months against Preston North End on 23 January 2016 and he assisted Alan Judge for one of Brentford's three goals in the victory. Tarkowski's subsequent departure from the club saw Barbet become Harlee Dean's partner in central defence through to the end of the 2015–16 season. He was sent off for the first time in his career after just five minutes of a match versus Sheffield Wednesday on 13 February, which Brentford eventually lost 4–0. On his return to the team in March, Barbet scored his first Bees goal with what proved to be a consolation in a 2–1 defeat to Charlton Athletic. He finished the 2015–16 season with 19 appearances.
