The striker headed in Matteo Guendouzi's cross after five minutes before poking home a brilliant move before half-time at Emirates Stadium.

Brentford's Alan Judge curled a superb 20-yard free-kick into the top corner after the break.

Substitute Alexandre Lacazette scored a third for Arsenal in stoppage time.

The Frenchman pounced on a loose ball and slotted home, before Alex Iwobi had a goal ruled out for offside.

Arsenal dominated the first half and looked comfortable at the start of the second before Judge's goal - his first in 942 days following a double leg break.

Yoann Barbet drew a save from Arsenal summer signing Bernd Leno before Canos dragged wide and Judge fluffed an effort.

Leno, making only his second start for the Gunners, had almost turned the ball into his own net early in the game after mis-controlling a pass.

Arsenal's Emile Smith Rowe was bright throughout, coming close in the first half on his full debut.

The 18-year-old was one of nine changes manager Unai Emery made to his starting XI following Sunday's Premier League win over Everton.

Brentford made seven changes as defender Moses Odubajo was handed a debut on his return to the club after recovering from a serious knee injury.

Arsenal have not lost a home match in this competition against a side from outside the top flight since 1983.

The draw for the fourth round will take place on Saturday.