Hull: (10) 24
Tries: Domic, Yeaman, Briscoe
Goals: Tickle 6 St Helens: (6) 12
Tries: Graham, Wellens
Goals: Tyrer 2
Hull finally kick-started their season with a stunning and deserved victory over Super League champions St Helens.
Saints took the lead with a James Graham try but Hull hit back through Sid Domic and some accurate kicking from Danny Tickle to lead at half-time.
The visitors lost Leon Pryce to the sin bin and Hull took advantage with 19-year-old Thomas Lee setting up tries for Kirk Yeaman and Shaun Briscoe.
Paul Wellens gave St Helens hope with a late try but Hull held on for victory.
It was a first home win of the season and for Hull, and sweet revenge against St Helens who had inflicted their heaviest-ever home defeat (46-0) on Hull last season and who also beat them in last season's Grand Final.
Hull have struggled all season in the absence of injured playmaker Paul Cooke but 19-year-old Thomas Lee was impressive at half-back, setting up both Yeaman and Briscoe for their tries.
The one dark spot of the evening for Hull was the head injury to Richard Swain.
The former New Zealand hooker looked out cold after banging his head in a tackle but was able to walk off the pitch.
Hull coach Peter Sharp
"There's more to come, I'm sure of that. There has to be. We have been showing signs over the last week or so that we were on the improve and we certainly improved dramatically tonight. "We have a history of playing a bit better against the so-called better sides and we were certainly up for the game.
"I've seen signs at training that we were on the improve and that things were starting to happen."
St Helens coach Daniel Anderson
"They made some big plays. I think that we had plenty of try-scoring opportunities in the second half but some big last-ditch tackles by Hull thwarted our points. "Personally I thought Hull were going to find some form. We spoke about how we were going to be to Hull, like Brisbane were for us, something to kick-start you in to the competition.
"We spoke about that before the game. They played with a resilience and a toughness that we know Hull are capable of."
Hull: Briscoe, Sing, Domic, Yeaman, Raynor, Lee, R. Horne, Dowes, Swain, King, Radford, Tickle, Washbrook.
Replacements: Tony, Manu, Godwin, Maiava.
St Helens: Wellens, Gardner, Gidley, Tyrer, Meli, Pryce, Long, Fozzard, Cunningham, Cayless, Gilmour, Bennett, Wilkin.
Replacements: Roby, Graham, Fa'asavalu, Sculthorpe.
Referee: R Silverwood (Dewsbury)