The former Derby ‘keeper was dismissed in the 67th minute for a foul on Jamie Ward just outside the box and the home side made their superiority pay in a game they dominated with late goals from Will Hughes and Chris Martin.
Hughes broke the deadock nine minutes from time before Martin sealed the win with Derby’s second in stoppage time.
Bournemouth were aiming to spoil the first anniversary of McClaren’s appointment by beating Derby in a competitive match for the first time since 1985 but they had a narrow escape in the 10th minute when Ward cut the ball back from the left and Craig Bryson fired over under pressure.
Cyrus Christie flashed a ball in from the right across the face of the Bournemouth six-yard box in the 19th minute but, although they were dominating possession, Derby were given a scare in the 23rd minute.
After they lost the ball out on the right, Junior Stanislas played an angled pass to put Callum Wilson in but the striker wasted a great chance by scuffing his shot at Lee Grant from 12 yards.
Bryson responded with a 20-yard drive that Camp saved at the second attempt and Ryan Shotton headed over a corner in the 29th minute following sustained home pressure.
Bournemouth were working hard to deny Derby space but Christie opened them up in the 38th minute with a powerful run that took him past two defenders before he fired just past Camp’s right-hand post.
McClaren made a change at half-time, replacing Jordon Ibe with Johnny Russell and the substitute made an early impact by blocking a clearance which almost fell for Martin.
Derby were still on top and another surging run by Christie down the right in the 62nd minute ended with the full-back squeezing the ball in to Martin who shot wide under pressure.
The game erupted in controversy in the 67th minute when Camp brought down Ward just outside the area and although the ball ended up in the net, referee Scott Mathieson brought play back before red-carding the ‘keeper, much to the delight of the home fans.
Derby’s players had been celebrating a goal and clearly felt advantage should have been played but Camp’s replacement Darryl Flahavan almost conceded straight away when Martin’s free-kick beat his dive but bounced away off his left post.
But Derby did not take long to make their man advantage count with a goal which arrived in the 81st minute when Hughes and Martin exchanged passes before Hughes drove the ball into the top left corner from 15 yards.
It left the visitors with no option but to chase the game and Simon Francis gave Derby a scare in stoppage time with a cross that fizzed dangerously across the face of goal, but Martin settled any nerves when he turned in Russell’s whipped ball in from the right.