Pearson's assistant manager, Chris Powell, will take charge of the team at Cardiff.
Club spokesman Paul Tyrrell said: "Derby County can confirm that manager Nigel Pearson will not be carrying out his duties at tonight's game - at the request of the club.
"Assistant manager Chris Powell will take charge of the team for tonight's Sky Bet Championship match at Cardiff City. The club will make no further comment at this time."
On the pitch Cardiff hope to welcome back top scorer Anthony Pilkington.
Pilkington missed the Bluebirds' first win in six matches - the 2-1 victory at Rotherham on Saturday - with a thigh injury suffered against Leeds a week earlier.
Aron Gunnarsson (calf) also missed out at Rotherham, but Stuart O'Keefe is expected to retain his place in midfield after impressing on his return following six weeks out with a broken arm.
Former Aston Villa defender Joe Bennett is again expected to be absent with the calf problem which has prevented him from making his Cardiff debut.
Derby have Johnny Russell back in contention for the trip to the Welsh capital.
The forward has missed the last four matches with a calf injury but he has resumed training and is set to return to the squad on Tuesday night.
James Wilson also has a chance of coming back into the reckoning. The on-loan Manchester United striker has sat out two games with a knock but he too has trained and he will be assessed.
However, Jason Shackell (calf), Craig Forsyth (knee) and George Thorne (leg) all remain sidelined for the Rams as they look for a first win in seven Sky Bet Championship outings.
- Cardiff have won five of their last nine home league games against the Rams, drawing three (L1).
- Derby have lost just one of their last six league games against the Bluebirds (W2 D3), though that defeat came in the most recent meeting in April last season.
- Derby have the worst shot conversion rate in the Championship this season, scoring with just 2.4% of their attempts.
- The Bluebirds have lost three of their last four games at home in league competition, winning the other vs Blackburn.
Referee: Geoff Eltringham
Assistants: John Law and Kevin Morris
Fourth Official: Brendan Malone
Cardiff City v Derby County
Tuesday 27th September. ko 7:45pm.