Gabriel Tamas was sent off for the home side 65 minutes in but after that Keith Andrews and Almen Abdi (his second) put Huddersfield to bed.
Prior to that, Troy Deeney and Abdi had seen goals cancelled out by Harry Bunn and Murray Wallace.
It was a little harsh on Huddersfield who started relatively brightly as James Vaughan headed a long throw over the top, but it did not take their opponents long to start posing questions.
Ikechi Anya fired across goal and wide following a Hornets counter-attack, before an unmarked Deeney headed a deep Daniel Tozser free-kick narrowly the wrong side of Alex Smithies’ far post.
Deeney came into the game having scored 11 goals in his last 11 appearances at Vicarage Road and after signing a new four-year deal in the build-up to the match to end speculation about his future, there was a sense of inevitability that the striker would continue his home hot streak.
He duly did, putting Watford into a 15th-minute lead when he calmly beat Smithies after being put through by a pin-point Tozser pass that bisected the Terriers defence.
Deeney almost added a second, clipping a shot into the side netting after a powerful run into the penalty area, before Huddersfield thought they had equalised when goalkeeper Heurelho Gomes was unable to hold a long-range shot from Conor Coady and Vaughan converted the rebound, only for it to be ruled out for an offside flag.
Watford should have doubled their lead shortly before half-time, though, when a fine deep cross from Tamas picked out the unmarked Fernando Forestieri but he headed over the bar.
Within three minutes of the restart though, Huddersfield were level when Gomes failed to deal convincingly with a Sean Scannell cross from his right and Bunn capitalised on the keeper’s loose parry, sweeping the rebound in to make it 1-1.
That goal raised question marks about the Hornets’ defending, but six minutes later the finger pointing was directed at the Town backline when, after the ball had broken Watford’s way following a challenge, Abdi strode through a big hole in the defence to net his first of the season.
Town were in no mood to lie down though, and in the 64th minute they levelled for a second time when Wallace rose well to head in a corner from the right.
The game appeared to have swung further in the Terriers’ direction a minute later when Tamas, who had already been booked for a foul on Bunn, committed another illegal challenge on the same player and could have no complaints about his red card fate.
But the rollercoaster nature of the match was summed up in the 68th minute when, after Smithies had produced a fine save to tip an Abdi free-kick behind, the Town keeper was helpless when the resulting corner was headed in by substitute Andrews.
Huddersfield tried their best to equalise for a third time but they were caught on the counter deep into injury-time as Tozser worked the ball to Abdi, who cut back on his right foot before curling home a superb fourth.