Chris Gunter battles for possession
It took a late flurry of goals to settle what had been a closely-fought game for long periods, with Billy Davies' side themselves coming close to taking the lead as Robert Earnshaw flicked a header against the bar.
Nigel Pearson's side had suffered a 5-1 defeat at the City Ground earlier in the campaign.
And they hit back in painful fashion for the 3,000 travelling Forest fans, as a close-range finish from Bruno Berner, a stunning free-kick from Paul Gallagher and an instinctive strike from Andy King saw Leicester power to victory in the final 20 minutes.
Forest suffered a nervous opening few minutes as Lee Camp was badly winded amid a melee when an early corner was delivered into the box. But, after lengthy treatment, the keeper was able to continue.
The game did have a slight edge to it, with Richie Wellens booked for a lunging tackle on James Perch, although Forest also had Earnshaw booked for kicking the ball away and Raddy Majewski for diving.
Majewski, the Polish midfielder, was the first to force a save from either keeper, with a driven volley from the edge of the box that he didn't quite connect with properly, giving Chris Weale a straightforward block.
But this was a cagey affair in which both sides produced the occasional bursts of passing football, without quite managing to make the breakthrough in the final third.
Earnshaw, who had tormented Leicester with a hat-trick at the City Ground, came close to breaking the deadlock as he flicked a header against the bar after connecting with a Majewski free-kick and, 30 seconds later, sent an over-head kick narrowly wide.
As the half came to an end it was Forest on top, with Chris Cohen seeing a powerful right-foot shot cleared by Waghorn, after a corner had only been half cleared and Majewski following suit with a long range strike that was also blocked amid a melee of players.
Majewski was a lively figure again as the second half began in pouring rain, giving Weale an awkward moment in the slippery conditions with a bouncing shot from the edge of the box.
Michael Morrison then sent a towering header rattling against the bar for Leicester – but his effort would have been ruled out for offside had it found the net.
A clumsy challenge by Earnshaw then had the Leicester fans calling for him to be sent off, following his earlier booking.
Referee Probert for once kept his cards in his pocket – but punishment was still dealt out as, from the resulting free-kick, Paul Gallagher swung the ball to the far post where Wellens clipped the ball back across goal – and Bruno Berner lashed home a close-range finish to put the home side ahead.
A foul on Perch gave Cohen the chance to deliver a free-kick into the box from the left and, when Earnshaw had flicked the ball cleverly back into the danger zone, Perch saw a close-range drive cleared off the line.
But, when substitute Tyson gave away a free-kick on the edge of the Forest box, the home side took full advantage, as Gallagher bent an unstoppable shot beyond Camp and high into the top corner.
Things get worse for Forest as Morgan blocked a driven shot from the advancing Berner, only for the ball to fall perfectly for Andy King, who flicked a shot beyond the stunned Camp.
Skipper Paul McKenna forced an acrobatic stop from Weale with a powerful strike from 25 yards, but by then it was too late for the Reds to force their way back into the game.