This was the first time since Peter Grant took over at Carrow Road that Norwich had scored more than a single goal in a game.
The Foxes kicked off attacking the River End goal, but it was former Leicester man Dion Dublin who produced the first shot on target when he forced Conrad Logan to tip the ball over the bar in the second minute.
Referee Darren Deadman awarded a goal-kick much to the annoyance of the home fans behind the goal.
After ten minutes Darren Huckerby played a one-two with Dickson Etuhu but his shot was cleared for a corner.
Iain Hume and Levi Porter went close for Leicester before Norwich captain Adam Drury limped off after 20 minutes and was replaced by Youssef Safri with Andrew Hughes switching to left-back.
Leicester took the lead in the 23rd minute when Patrick McCarthy's bullet header from Danny Tiatto's right-wing free-kick beat Lee Camp high to his right.
Josh Low's shot cleared the bar and Huckerby's shot was held by Logan before he became the third Norwich player to be booked for a foul.
As the game went into first-half stoppage time, Peter Thorne headed over, but there was still time for Carl Robinson to put the Canaries level with a well placed far post header from Huckerby's left-wing cross.
Six minutes into the second half Richard Stearman became the second Leicester booking.
Logan blocked Robert Earnshaw's shot and Thorne took a knock as he tried to make contact with the rebound.
In the 59th minute Safri won the ball on the halfway line and fed Earnshaw who raced goalwards and beat the advancing keeper with a left-foot chip from 16 yards.
Two minutes later Earnshaw got his head to Huckerby's cross but Logan saved.
In stoppage time Gareth McAuley was unlucky to see the ball fly into the net off his shin after Logan had got a hand to Earnshaw's goalbound right-foot shot from 12 yards.