The Wildcats recovered from 16-0 down to end a six-game winless streak at the KC Stadium.
Hull led 12-0 at the break thanks to tries from Danny Houghton and Jordan Rankin, before Jason Crooks gave the hosts a 16-0 lead after 50 minutes.
Both teams were reduced to 12-men with the sin binning of Crooks and Chris Riley, and it was Trinity who put that emotion to best use to respond through Richard Mathers, Daniel Smith and Lucas Walshaw to bring the teams all-square.
With seven minutes remaining Jarrod Sammut finished a sublime move to put Trinity six points clear before a fantastic Paul Sykes drop goal three minutes from time secured a memorable comeback.
Richard Agar was able to recall skipper Danny Kirmond to the starting line-up with Jacob Fairbank making his debut from the replacements bench.
It was a cagey start from both teams and it was the visitors who threatened first. The trio of Harry Siejka, Sykes and Sammut combined to create Hull problems and with the Hull defence reeling, McShane went on the short side and found Walshaw who dotted down in the corner only to be denied for a stud in touch by the touch judge.
It was a rare moment of excitement in a war of attrition in the opening quarter but Hull wrestled back the early ascendency from the Wildcats and got their rewards when Rankin popped up a pass to the alert Houghton who was in under the posts.
Washbrook made a crucial tackle to prevent Jordan Thompson racing through but the game was generally being played of the middle third of the pitch, a run of penalties provided Trinity with some attacking opportunity but they couldn’t crack the Hull defence.
With the interval rapidly approaching the Wildcats were hit by a hammer blow as Heremaia sold a dummy and broke clear, he had Rankin in support to stroll in under the sticks. Crooks converted once more and the black and whites had a 12-0 advantage at the break.
Trinity would have wanted to score first after the break but it was Hull who dominated the early exchanges and extended their lead in controversial circumstances. The Airlie Birds had the overlap on the right hand side and the pace of Shaul got him on the outside of Walshaw who clung on well. However, Shaul popped out a pass to Crooks that appeared a yard forward and the winger was in.
It made a difficult task even harder for the Wildcats but they responded on 55 minutes, Kirmond making the half break, getting the ball free from the tackle to Matty Ryan who gave Mathers the simple task of going over in the corner.
If the first half had been a little tame in terms of excitement the second half exploded into life on the hour mark as Chris Riley and Jason Crookes exchanged punches and both were sent to the sin bin for 10 minutes.
It was the visitors who used the fire in their belly to best effect, Smith taking a carry full of determination and nobody in black and white could deny the prop forward getting to the try line, all 24 players coming together after the score to continue the ill-feeling.
Minutes later and the teams were all square, Washbrook throwing the dummy to make a break and timing a pass to perfection for Walshaw who summed up his options and took on Shaul at the corner to score. Sammut had the whistles of the Hull fans in his ears but he nailed the touchline conversion.
Siejka had a crack at a drop goal with 15 minutes left that he hooked wide before Crooks missed the chance to put Hull in the lead with a 25 metre penalty.
The crucial try came seven minutes from the end, an offload from Moore creating the disarray in the Hull defence and after Sykes and Godinet combined, it was left to Washbrook to put Sammut in under the posts.
A Lee Smith drop goal won the game last year and Sykes, back tracking and under pressure hit a fantastic 30 metre one-pointer to secure the win and spark huge celebrations in the away end.
Wildcats: Sammut, Mathers, Ryan, Walshaw, Riley, Sykes, Siejka, Anderson, McShane, Scruton, Washbrook, Kirmond, Smith. Replacements: Godinet, Moore, Molloy, Fairbank.
Hull FC: Shaul, Crookes, Crooks, Yeaman, Talanoa, Rankin, Miller, Paea, Houghton, Bowden, Ellis, Hadley, Westerman. Replacements: Heremaia, Thompson, Paleaaesina, Tuson.