The Arsenal right-back was powerless to stop the ball spinning past Bernd Leno and into the goal.
However the goal was symptomatic of a poor start for the 'Gunners', with Leicester having the better of the early chances at the Emirates Stadium.
Chilwell, who recently returend from international duty having made his full debut for England bombed forward up the left in the 30th minute.
His touch initially took him beyond Arsenal's Spanish defender, who had appeared to recover well, but the only block he could get on the Leicester youth product's low cross diverted the ball into his own net.