The meeting took place in Brentford and ended in favor of the hosts - 2: 0.
Sergi Kanos scored in the league debutant in the 22nd minute, and Christian Nergor scored in the 73rd minute.
Last season, Brentford finished third in the Championship and moved up to the elite division, while Arsenal finished eighth in the Premier League.
Earlier it was reported that the Brentford footballer scored the first goal of the new Premier League season.