Steve McClaren's side leapfrogged Watford and moved to the summit after the Bloomfield Road win - which came thanks to Chris Martin's penalty.
Blackpool have registered just one win this season and sit bottom, meaning Derby were heavy favourites to triumph on the road.
But the hosts were better in the first half, with Nathan Delfouneso going closest when he fired over.
Johnny Russell was brought down by Tony McMahon in the area with just nine minutes to play, though, and Martin slotted the resultant spot-kick.
Watford lost their grip on the league lead with a 2-2 home draw against Nottingham Forest - Michail Antonio equalising twice for the visitors.
Manager-less Birmingham City were unlucky to lose 1-0 at Blackburn Rovers.
Ben Marshall scored the game's only goal in the 51st minute, before Neal Eardley was sent off for the visitors.
Birmingham - who parted company with Lee Clark on Monday - hit the crossbar in stoppage time through substitute Andrew Shinnie.
Wolves closed to within goal difference of the third-placed Middlesbrough after beating them 2-0 at Molineux - Bakary Sako and Nouha Dicko the scorers.
Cardiff City climbed to 10th with their second straight win under new manager Russell Slade - a 3-1 home success against Ipswich Town.
Daryl Murphy gave Ipswich a 29th-minute lead, but goals from Peter Whittingham, Federico Macheda and Adam Le Fondre sealed Cardiff's win.
Leeds United are still searching for their first win under coach Darko Milanic but did come from behind to claim an impressive 1-1 draw at Norwich City.
Souleymane Doukara struck Leeds' 63rd-minute equaliser from 20 yards, cancelling out Russell Martin's opener.
Norwich boss Neil Adams revealed afterwards that striker Cameron Jerome had "complained of a racist remark" at Carrow Road on Tuesday.
There was late drama at the New York Stadium, with Dan Burn's 90th-minute equaliser earning Fulham a point in a thrilling 3-3 draw with Rotherham United.
Rotherham led on three occasions but Burn's last-gasp effort gave Fulham a point that pushed them to within goal difference of leaving the relegation zone.
Elsewhere, Neil Lennon was unable to steer Bolton to successive wins, as they slumped to a 2-1 loss at Charlton Athletic.
Brett Pitman scored twice in AFC Bournemouth's 3-0 win over Reading and Huddersfield Town drew 1-1 with Brighton and Hove Albion.
And there were goalless draws between Brentford and Sheffield Wednesday, and Wigan Athletic and Millwall.
Get the best features, fun and footballing frolics straight to your inbox every week.
Thank you for signing up to Four Four Two. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.