Although Nicklas Bendtner was unlucky to put through his own goal in the first half, Derby underlined their superiority against one of McClaren’s former clubs with second-half strikes from Tom Ince and Will Hughes.
It was a sixth straight league victory for the Rams and moved them into the top six for the first time this season.
Forest’s four match unbeaten run came to an end and although they competed well in the first half, they created little as Derby kept a fourth consecutive clean sheet and seventh in nine games since McClaren returned to the club in October.
Forest probably sensed it was not going to be their day before a ball had been kicked when November’s Championship Player of the Month Henri Lansbury was injured in the warm-up and replaced by Mustapha Carayol.
It was Carayol who threatened to open Derby’s defence with a powerful run that ended with a shot blocked by Richard Keogh before a flare-up involving Bradley Johnson and Ben Osborn in the ninth minute resulted in bookings for both players plus yellow cards for Darren Bent and Damien Perquis.
Bent was close to connecting with a low cross from Chris Baird before Marcus Olsson glided past a defender on the left but could not pick out a white shirt.
Carayol had a shot deflected behind when Forest broke dangerously in the 25th minute and Bent was lucky to stay on the field a minute later after catching Eric Lichaj late.
The game had lacked quality so it was appropriate that the goal that gave Derby the lead in the 33rd minute was a scrappy one with a flick on by Johnny Russell from a corner ricocheting off Bendtner’s head and past Vladimir Stojkovic.
Forest could certainly count themselves unlucky but they had a chance to equalise in stoppage time when the ball broke to Matty Cash 15 yards out but his shot lacked power and Scott Carson dropped to his left to save.
Bendtner almost scored a second own goal in the 52nd minute when he headed a free-kick against the bar but Derby made it two in the 55th minute when Baird’s precise pass down the right channel allowed Ince to slip past Lichaj and turn inside Michael Mancienne before lifting the ball past Stojkovic from 12 yards.
Any chance of a Forest recovery vanished in the 64th minute when Hughes set up Russell and although Stojkovic thrust out his right foot to make a great save, Hughes followed up to net the rebound.
It was then a case of damage limitation for Forest but Derby knew they had done enough to give their fans an early Christmas present.