The visitors took the lead just after the half-hour mark when Simon Cox scruffily found the net against the run of play.
Another fortuitous goal came just before the break when Henri Lansbury's volley was cleared off the line but straight to Jamie Mackie, who picked out the top corner.
Here, Sports Mole picks the bones out of a first win for Forest against Leicester in five attempts.
On target 2
On target 5
Was the result fair?
Yes. Leicester may have had over double the shots that Forest did but they only managed two on target. Forest's two goals did come against the run of play in the first half but Leicester did nowhere near enough after the interval to earn a point. In fact, Forest perhaps looked the more likely to score on the counter-attack.
Nigel Pearson's side went into the match on a run of four successive wins in all competitions but saw that and their unbeaten home run fall to pieces in front of the biggest crowd at the King Power Stadium for years. Anthony Knockaert was bright early on and his cleverness set up chances for Nugent and Lloyd Dyer. Then came the sucker-punch of Cox's opener and the Foxes never really recovered from that. Nugent should have at least put the penalty on target but his casual miss just summed up a bad day at the office for Leicester. Burnley and QPR, the other two early pacesetters, could only draw today, so the Foxes might feel a touch lucky in that respect.
As mentioned above, today's result broke a couple of unfortunate records for Forest as they stopped their losing run both form-wise and against Leicester. Billy Davies's side were on the back foot almost instantly but recovered well and showed Leicester how to take their chances. Mackie's finish was especially good as he had no time to think about it but still found the top corner with several bodies around him and on the line. From then on, Forest would have expected more of a Leicester fightback but it never really came.
Sports Mole's man of the match
Jack Hobbs: The Forest centre-back settled another East Midlands derby earlier in the season by heading in the one and only goal against Derby and today he again rose to the big occasion with a towering performance at the back for the visitors.
Clear winner here in Nugent. If he had scored from 12 yards with 20 minutes left, then Leicester would have been buoyed and had plenty of time to score an equaliser and maybe even a winner.
Lee Mason dished out five yellow cards because of some tasty tackling. Marcin Wasilewski was lucky in the first half to only get a booking when he left the ground to dive in two-footed on a Forest man but did not get anywhere near the man or ball. The penalty decision was a bit soft but David Vaughan did come through the back of Danny Drinkwater and that's always going to spell trouble.
Leicester: A two-week international break is next up and after that Leicester travel to Ipswich Town.
Forest: Next up for Forest are league leaders Burnley, who head to the City Ground in a fortnight.