A noon kick-off appeared to suit the Gunners better in the west London sun as Gabriel Martinelli was given time and space in the box to fire off a warning shot, which David Raya gathered after the Brazilian lost his footing in the shot.
The Bees goalkeeper could do nothing about William Saliba’s opener on 17 minutes as the defender rose highest to flick Bukayo Saka’s corner across goal and in off the far post, with goalline technology confirming it had narrowly crossed the line.
Arsenal took a firm grip of proceedings and doubled their advantage from another cross into the box, this time Granit Xhaka expertly picking out Gabriel Jesus for a powerful header before the half-hour mark.
The points were secured only minutes into the second half as Fabio Vieira, on his first Premier League start, fired a left-footed stunner from outside the box that crashed into the net via the post.
Jesus and Bukayo Saka both saw efforts to make it four denied by Raya as Arsenal cruised towards the final whistle, Brentford failing to get going from first whistle to last.
After the international break, Tottenham and Liverpool travel to the Emirates Stadium either side of a Europa League meeting with Bodo/Glimt in what will be not only a test of the Gunners’ top-four credentials - but their dreams of putting up a serious bid for the title.