A game that typified local derbies - full of commitment but short on quality - was settled 12 minutes from the end when Rob Hulse headed his seventh goal of the season.
It was enough to condemn high-flying Forest to their first Championship away defeat of the campaign and eased Derby's relegation fears.
The end of Forest's 19-match unbeaten run in the League was made even harder to swallow because the goal was set up by former City Ground favourite Kris Commons.
It was one of the few things of note he did in the game but his delivery for the free-kick was excellent and Hulse's head did the rest.
Derby deserved their first Championship home victory since late November by virtue of the energy and determination they showed which denied Forest the space to impose their passing game on the contest.
Although former Derby striker Rob Earnshaw had a shot headed off the line early on, the home side built up pressure that would have been rewarded but for another ex-Pride Park old boy, Lee Camp.
The Forest keeper arched backwards to tip over a Jake Buxton header and then did even better to plunge low to this right to deny Shaun Barker.
The centre-half, who was born just outside Nottingham, had an outstanding game in a Derby defence which limited a free-scoring Forest side to only a few openings.
Paul Anderson was twice denied by brave blocks and Stephen Bywater made a reflex save to keep out a Dexter Blackstock header in the 57th minute.
As the temperature on the pitch began to rise - eight players were booked - Derby silenced the visiting fans in the 78th minute when James Perch fouled Gary Teale out on the right and Commons provided Hulse with a chance he flashed into the top right-hand corner.
There was a flare-up on the touchline near the end but nothing like the one at The City Ground in August when Forest celebrated victory. This time it was Derby who took the East Midlands honours.