Goals from Nahki Wells, Jamie Paterson and Flo Bojaj give Huddersfield their first win in four matches and halted Reading’s five-match unbeaten run.
Wells capitalised on Andrew Taylor’s errant backpass to slot the Terriers ahead shortly after the restart.
Paterson doubled the hosts’ advantage when he fired in from Sean Scannell’s superb low cross.
Bojaj turned in Dean Whitehead’s cross for his first professional goal before Ola John’s late consolation.
It was a first win for Huddersfield in four meetings with Reading this season, having drawn the reverse league fixture 2-2 and lost to the Royals in the FA Cup third round after a replay.
David Wagner’s side stay 18th but are now seven points clear of relegation, while Reading fall three places to 14th and are now just two points ahead of the Terriers, albeit with a game in hand.
Huddersfield head coach David Wagner: “We deserved this win from the first minute. For large parts of the game there was only one team which tried to invest something in the offence.
“We’ve played better football in games this season, but to score three goals against Reading is massive for us.”
Reading manager Brian McDermott: “I picked the team with a lot of the players who will be involved on Friday (in the FA Cup against Crystal Palace).
“There was nothing in the game for 50-odd minutes and they scored and it’s not been the greatest night.
“It was a tricky night for me to try and pick the team and make sure we were really competitive. I thought we were competitive, the players we put out, some haven’t played for a while.”