The Giants looked the better team before the break, with Martin Aspinwall and Chris Nero both going over.
But Hull, who had slid down the table after losing six of their last seven matches, hit back in the second half.
Nathan Blacklock and Kirk Yeaman edged Hull ahead before Richard Horne went over to put the visitors on course for a valuable victory.
Hull caretaker coach Richard Agar "It was just the sort of win we needed. We felt that we had a good start to the game after a good week of preparation, but we were then disappointed with the last 30 minutes of the first half.
"I thought we were getting lots and lots of effort from quite a few players but I thought we had one too many passengers.
"That was passed on to the players at half time and we were delighted with the response in the second-half."
Huddersfield: Reilly, Aspinwall, Evans, Nero, Gardner, Thorman, Paul, Crabtree, Drew, Jackson, Smith, Jones, Wild.
Replacements: Donlan, March, McDonald, Raleigh.
Hull: Tony, Blacklock, Yeaman, Domic, Dixon, Cooke, R. Horne, Dowes, Swain, Carvell, Radford, Hill, Chester.
Replacements: Thackray, Brough, Wheeldon, Whiting.
Referee: P Bentham (Warrington).