Goals from popular old boy Gary Taylor-Fletcher and Leicester skipper Wes Morgan condemned Town to defeat in their final home game of the season.
There was a strike in each half as the Premier League-bound visitors forced a 14th away win and 30th league success in all.
With Leicester having already sealed the Championship title and Town ensuring survival in the second tier, both managers made changes.
Mark Robins brought in centre-back Peter Clarke, midfielder Duane Holmes and forward Sean Scannell, with Murray Wallace, Ollie Norwood and Danny Ward dropping to the bench.
It was a second start for American teenager Holmes, and his first since the home derby win over Leeds in October.
Leicester boss Nigel Pearson called up six new faces to his starting side, including Taylor-Fletcher and New Zealander Chris Wood.
Andy King had a header held by Alex Smithies and Wood had a shot blocked as the visitors fashioned the first two chances of the game.
Town were seeing plenty of the ball in the opening stages, but the only genuine opportunity, a long-range shot by Adam Clayton, flew over.
At the other end, Matty James unleashed a stinging 24th-minute effort which beat Smithies but crashed down off the bar and was cleared.
Leicester finally got the goal they had been threatening in the 31st minute as the lively James broke from midfield and picked out Lloyd Dyer, from whose pass Taylor-Fletcher shot home.
Town fans were growing frustrated by their team's tendency to stray offside, but they were out of their seats four minutes before the break, when Adam Hammill's shot was cleared off the line.
Dyer had two separate shots parried by Smithies as Leicester started the second half on the offensive.
Then skipper Clarke made a timely challenge to thwart the Leicester wide man as he latched on to a through ball.
Norwood replaced Holmes in the 65th minute as Town manager Mark Robins sought some fresh impetus.
But Leicester forced their second goal of the afternoon when skipper Wes Morgan shot home from a corner in the 74th minute.
Town made a double change straight after, with Joe Lolley replacing Hammill and 17-year-old Philip Billing coming on for Jonathan Hogg to make his debut.
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