Leicester took their first Championship victory under Gary Megson as Sheffield Wednesday paid the price for some charitable defending at Hillsborough.
A Gareth McAuley header and an Akpo Sodje own goal in the opening 13 minutes gave the Foxes a first away victory in the league.
Both goals came from right-wing corners, Wednesday having no answer to Alan Sheehan's left-foot delivery.
Leicester keeper Marton Fulop made his only save with 13 minutes to go.
Wednesday boss Brian Laws:
"Everybody will look at every club that is not doing well and will put the manager under pressure.
"What we will do is work as hard as we've ever done before to put that right - the only time it changes is when the chairman does the changing.
"I was good enough last year and I'll be good enough this year."
Leicester boss Gary Megson, a lifelong Owls fan:
"It's purely and simply about doing a job for the club that employs me and it's a great result for me and a great result for the club.
"To win 2-0 against a team that's been doing very well in the last few games is a great testament to the players. They all showed great effort."
Sheff Wed: Grant, Bullen, Gilbert, Hinds, Michael Johnson (Beevers 38), Whelan, Tudgay, Esajas, Kavanagh, Burton (Jeffers 63), Sodje (O'Brien 63).
Subs Not Used: Burch, Lunt.
Leicester: Fulop, Kisnorbo, N'Gotty, McAuley, Stearman, Chambers, Newton, Sheehan, King (Kenton 74), Hume (Campbell 61), Fryatt (Cort 61).
Subs Not Used: Henderson, Kishishev.
Goals: McAuley 7, Kisnorbo 14.
Ref: Andre Marriner (W Midlands).