Elias Kachunga was the man to end a barren scoring run that, by the time he tapped in early on, had stretched to 648 minutes.
Clearly buoyed to end a seven-game drought, Town netted again through Aaron Mooy before half-time.
Laurent Depoitre’s fourth goal of the season and a Mooy penalty then rounded off the victory on an afternoon when Jonathan Hogg and Troy Deeney were sent off.
Town’s goal famine on the road ended in the sixth minute. It was the scruffiest of scruffy goals but no-one in those famous blue and white stripes or their vociferous travelling support cared a jot.
After Watford had two attempts at clearing a Chris Lowe corner, Aaron Mooy lobbed the ball back into the area.
Collin Quaner, initially stood offside, then headed back across goal for Laurent Depoitre to get a touch before Kachunga tapped in from a yard out.
Midway through the second half, Huddersfield doubled their advantage as Quaner drilled a low cross for Mooy to tap in.
Watford’s afternoon went from bad to worse when Troy Deeney was rightly sent off for a dreadful lunge at Quaner on 33 minutes
Huddersfield made their numerical advantage pay early in the second half when Laurent Depoitre fired in following a poor clearance by Sebastian Prodl.
Jonathan Hogg’s dismissal just after the hour for a second booking, incurred for a clumsy challenge on Richarlison, gave Watford hope that rose further when Abdoulaye Doucoure fired in from 20 yards.
Town weathered a stint of Watford pressure and added a fourth a minute from time when Depoitre was fouled by Doucoure and Mooy fired in the penalty.
After four months and 648 minutes, Huddersfield Town’s goal famine on the road ended in style as David Wagner’s men ran riot.
The goal that broke the deadlock won’t win any prizes as the best of the month, Collin Quaner being offside in the build-up and Elias Kachunga being the third Terriers man to touch the ball inside the six yard box.
But none of the 2,300 Town fans cared after such a long wait to see their side score away from the John Smith’s Stadium.
Typically, after going seven games without finding the net, Town went on to more than double their goal tally in fine fashion.