Duncan Watmore's double sank Huddersfield to give Chris Wilder his first win as Middlesbrough manager at the third attempt.
Jonny Howson sent Isaiah Jones away down the right and his cross picked out Watmore unmarked to sidefoot Boro ahead.
Former Terriers midfielder Matt Crooks then played a ball in behind Town's defence for the winger to beat goalkeeper Lee Nicholls with a fine lob.
Huddersfield rarely threatened, but pulled one back deep in stoppage time through Luke Daniels' own goal.
The Terriers kicked off unbeaten in their past five home matches, including four successive clean sheets, but conceded when Watmore netted with the first chance of note.