Alate Alexandre Lacazette strike gave Unai Emery his first away win as Arsenal manager against a Cardiff side that twice drew level.
Victor Camarasa and Danny Ward had responded to goals from Shkodran Mustafi and Pierre-Emerick Aubameyang and give Cardiff the hope of getting a draw.
Arsenal looked good on the ball but Emery still has plenty of work to do defensively as they gave too much space for the Cardiff forwards.
Lacazette capped an excellent display in his first start of the season by cracking the ball into the roof of the net from a tight angle.
