Owen Garvan's second of the season and a goal for Ricardo Fuller on his debut gave Ipswich the points they needed to keep their slim Coca-Cola Championship play-off hopes alive.
The Blues toiled for much of a lacklustre encounter ut upped the pace decisively after the break as Garvan turned home from a half-cleared Darren Currie corner and then the same player set up Fuller for the second late on.
Fuller was given his debut after receiving a work permit to complete his one-month loan from Southampton and he was partnered up front by 18-year-old Danny Haynes, who returned from an ankle injury.
A two-game suspension meant Leicester were without captain and central defender Paddy McCarthy, while Paul Henderson deputised in goal again for the injured Rab Douglas.
The Foxes started better - and after two minutes, Canadian midfielder Iain Hume drilled a right-footed effort which tested goalkeeper Shane Supple's early handling.
Then Nils-Eric Johansson should have done better on 13 minutes when he glanced Joey Gudjonsson's corner wide.
It was a promising enough opening - and with both sides showing a willingness to get forward, it seemed only a matter of time before the game burst to life.
But all too often after that the ball from both sides in the final third of the pitch lacked precision.
Johansson became the first player booked after 23 minutes when he stuck out a hand to stop an Ipswich pass finding its target.
That was the signal for a scrappy spell as the referee was forced to break up the action at regular intervals for a series of needless fouls.
Scott Barron, Richard Stearman and Garvan were all reckless before Danny Tiatto crunched Fabian Wilnis to the ground as the half drew to a disappointing close.
Then Richard Naylor got on the end of a rare chance a minute before the break - but his header was off target.
It was poor fare for the 24,000 fans packed into Portman Road - but finally six minutes after the break they were given something to shout about.
Currie was first to react as Leicester failed to clear his inswinging corner - and when he put the ball back into the box at the second attempt, Garvan was on hand to fire into the bottom corner.
Leicester sought to hit back immediately, and Matt Fryatt was just off target from 12 yards.
The same player then saw a 25-yard pile-driver blocked by Jason De Vos with 13 minutes left - but it was all in vain.
Four minutes from time, Fuller made sure of the points as he arrived unmarked to guide home another Currie corner.
Teams
Ipswich Supple, Wilnis, De Vos, Naylor, Richards, Currie,Garvan, Westlake, Barron, Haynes (McDonald 66), Fuller.
Subs Not Used: Price, Magilton, Sito, Proudlock.
Booked: Fuller.
Goals: Garvan 52, Fuller 86.
Leicester Henderson, Stearman, Kisnorbo, Gerrbrand, Johansson,Maybury, Gudjonsson, Hughes (Hammond 71), Tiatto (Williams 70),Hume (O'Grady 78), Fryatt.
Subs Not Used: Logan, Sylla.
Booked: Johansson.
Att: 24,861
Ref: P Taylor (Hertfordshire).