Arsenal are into the EFL Cup fourth round after Christian Fuchs' own goal and a late effort from Eddie Nketiah handed them a 2-0 win at the King Power Stadium.
Mikel Arteta made seven changes to the side that beat West Ham in the Premier League on Sunday (AEST) and his new-look XI struggled to lay a glove on the hosts during a tepid first half.
They improved after the break, though, and opened the scoring shortly before the hour mark when Fuchs inadvertently put through his own net after Nicolas Pepe's shot had come back off the post.
Nketiah bundled home from close range in the 90th minute to seal the win and ensure Arsenal made it three wins from three at the start of the 2020-21 season.
Both goalkeepers were called into action inside the opening 10 minutes, Danny Ward tipping over Reiss Nelson's fizzing drive from distance and Bernd Leno denying Kelechi Iheanacho at the other end.
The lively Nelson missed a glorious opportunity to open the scoring shortly after the half-hour mark, firing wide from 12 yards after finding space at a corner.
Leicester almost went into the interval ahead but James Maddison's curled effort from 20 yards crashed back off Leno's left-hand post.
After a sedate opening to the second period, Arsenal forged ahead in the 57th minute. Pepe's initial shot was pawed away by Ward, but the Ivorian's follow-up shot from an acute angle flew back off the post into Fuchs and over the line.
Wes Morgan denied Arsenal a second, heading Nketiah's looping effort off the line, while Ayoze Perez inexplicably headed wide 10 minutes from time in what was comfortably the Foxes' best chance of the game.
Nketiah then added Arsenal's second late on, scuffing home from inside the six-yard box after substitute Hector Bellerin's mazy run, with Daniel Amartey somehow failing to clear the danger.
What does it mean? Much-changed Arsenal cruise through
The Gunners barely had to get out of second gear to ease past Brendan Rodgers' insipid side.
Arteta will be relieved his decision to shuffle his pack did not backfire, with his much-changed side ensuring the club have now progressed into the EFL Cup fourth round in 17 of the last 18 seasons.
Nketiah ends mixed display on a high
The highly rated 21-year-old has now scored in consecutive games following his winner against West Ham at the weekend.
He was not at his best against Leicester - making the fewest passes and having the fewest touches of any Arsenal starter - but he showed a poacher's instinct with that late goal.
Iheanacho struggles in rare start
The Nigerian international started just 16 games last season and he is unlikely to replace Jamie Vardy any time soon if he continues to put in displays as ineffectual as this. He had one shot on target and completed just 12 passes, comfortably the lowest of Leicester's starters.
Both sides are back in Premier League action next, with Leicester travelling to Manchester City on Sunday and Arsenal visiting champions Liverpool a day later.