Leicester ran out convincing winners as Norwich's 13-game unbeaten run came to an abrupt end.
The home side almost took the lead when Stephen Clemence's volley was deflected over the bar before Iain Hume netted the Foxes' first goal from close range.
Steve Howard doubled the lead with a low left-footed shot into the corner before Norwich's Darel Russell was sent off for a tackle on Richard Stearman.
DJ Campbell then fired in from 12 yards and Stephen Clemence got the fourth.
Leicester boss Ian Holloway:
"At last the players had a day they can enjoy but what's most important is what happens next week when we have a massive game against Coventry.
"When we score first we are not a bad team but when we concede first we are pigging awful and that's got to change.
"We've got some fantastic players but at the moment they are not very consistent - and that has to change."
Norwich manager Glenn Roeder:
"It's very painful, it's been a long time since we've been beaten and the manner we have been beaten today has been very painful.
"But the players are human and I suppose you have to allow them an off day.
"But we have to be men about this, take it on the chin and not cry like little boys."
Leicester: Alnwick, Stearman (James Chambers 62), Kisnorbo, McAuley, Mattock (Laczko 24), Clapham, Oakley, Clemence, Hume, Campbell (Fryatt 85), Howard. Subs Not Used: Hayles, N'Gotty.
Booked: Hume, Kisnorbo.
Goals: Hume 22, Howard 57, Campbell 77, Clemence 82.
Norwich: Marshall, Otsemobor, Shackell, Doherty, Camara (Cureton 72), Croft, Fotheringham, Russell, Henry (Pattison 62), Dublin, Evans. Subs Not Used: Gilks, Pearce, Gibbs.
Sent Off: Russell (60).
Booked: Fotheringham, Dublin.
Ref: Clive Oliver (Northumberland).