The Foxes could have slipped into the bottom three with a defeat but they extended their unbeaten run to four games thanks to strikes in either half from Andy King and Steven Howard.
Darius Vassell had a goal disallowed before King broke the deadlock with a calm finish after he had ran on to Richie Wellens' pass.
Derby had opportunities to equalise, though, with Paul Green particularly culpable as his unmarked header missed the target.
Howard wrapped up the points when he netted from the penalty spot after Kyle Naughton was fouled by Kris Commons in the area.
The result sees Leicester move five points clear of the relegation zone whilst promotion-chasing Derby slipped eight points behind second-placed QPR.
Source: PA
