Boro fell two goals behind in the first half at Pride Park after goals from strikers Lee Gregory and Colin Kazim-Richards.
The visitors did manage to pull a goal back before the break through Neeskens Kebano but weren’t able to build momentum after the interval.
Neil Warnock’s side have now gone five games without a win and slipped six points adrift of the Championship play-off places.
Boro will now hope to get back to winning ways when they host Huddersfield on Tuesday – but will have to manage without new signing Yannick Bolasie.
The winger missed the Derby match with a hamstring issue and is set to be sidelined for a while.
Our Boro writer Joe Nicholson has dished out his marks from the fixture – scroll down and flick through our gallery to see them:
. DERBY, ENGLAND - FEBRUARY 13: Kamil Jozwiak of Derby County is challenged by Neeskens Kebano of Middlesbrough during the Sky Bet Championship match between Derby County and Middlesbrough at Pride Park Stadium on February 13, 2021 in Derby, England. Sporting stadiums around the UK remain under strict restrictions due to the Coronavirus Pandemic as Government social distancing laws prohibit fans inside venues resulting in games being played behind closed doors. (Photo by Mark Thompson/Getty Images)
Kamil Jozwiak of Derby County is challenged by Neeskens Kebano of Middlesbrough. Photo: Mark Thompson
. Marcus Bettinelli - 5
Couldn’t do much about either goal and didn’t have many saves to make in the second half when Derby dropped off. 5 Photo: Alex Pantling
. Darnell Fisher - 5
Was caught out of position a couple of times and had to make a couple of fouls to prevent Derby attacks. 5 Photo: Getty Images
. Paddy McNair - 5
Endured a tough first half against Derby’s front two. Moved into midfield after half-time and saw more of the ball. 5 Photo: Alex Pantling
. Anfernee Dijksteel - 4
Unconvincing at centre-back as Derby launched balls forward to their front two in the first half. 4 Photo: George Wood
1. Marcus Bettinelli - 5
Couldn’t do much about either goal and didn’t have many saves to make in the second half when Derby dropped off. 5 Photo: Alex Pantling
2. Darnell Fisher - 5
Was caught out of position a couple of times and had to make a couple of fouls to prevent Derby attacks. 5 Photo: Getty Images
3. Paddy McNair - 5
Endured a tough first half against Derby’s front two. Moved into midfield after half-time and saw more of the ball. 5 Photo: Alex Pantling
4. Anfernee Dijksteel - 4
Unconvincing at centre-back as Derby launched balls forward to their front two in the first half. 4 Photo: George Wood