Derbyshire has only started six games this season but his Saturday goal against Birmingham ended Forest's 13-match winless run and the former Blackburn striker's rich vein of form continued at a subdued Elland Road.
With a visit to Bournemouth and a home task against Brighton to come, Forest are just one point outside the top six after winning 2-0 in West Yorkshire.
They made a dream start with two goals from Derbyshire in the first 16 minutes.
The game was just one minute and 32 seconds old when Scotland international Jamie Mackie threaded the ball through the centre of the Leeds defence to Derbyshire, who took it forward before picking his spot.
Forest doubled their lead when Derbyshire took advantage of a slip-up by Leeds defender Scott Wootton by clipping an angled shot past Jack Butland from 12 yards.
It was a painful wake-up call for Leeds who had won their last two matches, albeit against strugglers Blackpool and Barnsley.
Derbyshire, who scored Forest's winner against Leeds in December, escaped his marker again before heading just over the bar and, with Forest very much on top, Butland had his hands stung by Stephen McLaughlin's speculative shot from 30 yards.
There was anxiety for Forest when Derbyshire and Jamie Paterson needed lengthy treatment after a collision but they recovered sufficiently to carry on.
Five minutes before the interval Leeds' top scorer Ross McCormack was inches away from netting his 30th goal of the season in all competitions.
Mackie handled just outside the penalty box and McCormack's rasping free-kick zipped fractionally outside the near post.
Leeds' defence remained vulnerable and Butland had to move smartly to his left to hold Osborn's low drive from distance.
Leeds needed to summon a massive improvement in the second half and they began with more purpose.
Rodolph Austin had a shot blocked in the goalmouth, Luke Murphy's deflected effort made keeper Dorus De Vries change direction to save and the keeper then did well to claw McCormack's bending free-kick round a post.
Matt Smith's arrival from the bench in place of Noel Hunt drew approval from the home crowd on the hour mark and Leeds later brought on Danny Pugh and young midfielder Alex Mowatt in the hope of turning the game round.
Leeds enjoyed more possession in the second half but Forest's defence proved hard to break down, with Leeds lacking genuine quality which can only be rectified by summer recruitment.
Forest replaced injured keeper De Vries with Bulgarian Dimitar Evtimov 10 minutes from the end and he made a smart save from Smith's stoppage-time header.