Wade McKinnon's brace helped Hull FC extend St Helens' winless run to four games in a convincing victory at Langtree Park.
The former Wests Tigers full-back took his personal tally to four for the season, while Jordan Turner also scored in Hull's second successive win.
Second-row Danny Tickle was inspired with the boot, kicking five goals.
For Saints, Ade Gardner and Tony Puletua ran in tries, while Jamie Foster kicked one goal.
Despite a nervy opening for Royce Simmons' Saints, they made early chances through Jonny Lomax's probing, and prop Anthony Laffranchi was unfortunate to miss out when he failed to clutch the half-back's pass.
However, they did open the scoring when Barrow-born Gardner, who missed much of last season through injury, raced in after a move involving Lomax, Lance Hohaia and Michael Shenton.
That score settled some of the frustration around Saints' new home, but the optimism diminished when McKinnon notched the first of his two tries with a jinking run from full-back.
But, like his counterpart, Tickle was off target with the conversion.
After the break, it was again Saints who made the livelier start, and they were first to register a score when Puletua darted over, Foster successfully converting this time.
Yet Hull, coached by Simmons' Australian compatriot Peter Gentle, then stepped up a gear to take control.
First, the pacy Turner intercepted a Perry flick pass and galloped the length of the field to restore parity, and the Airlie Birds took the lead when Tickle notched his second goal of the night.
Tickle's accuracy with the boot - and Saints' indiscipline in giving him the opportunities to demonstrate it - further contributed to the home side's downfall, and McKinnon's second try was merely the icing on the Black and White cake.
VIEWS FROM THE DRESSING ROOM
St Helens coach Royce Simmons:
"There was no communication out there whatsoever. We were lost and I am the coach and I did not know what we were doing at different stages. It was not what we planned to do.
"We played sideline to side, and never established any go forward to play off the back of. We chased the ball all over the park, it was all over the shop. That all comes back to communication. A couple of close losses in the last couple of weeks creates a bit of doubt - and the first thing that goes then is communication.
"We ran the ball on the last tackle two or three times, and our kicking game was not as good in the second half. I thought we were reasonable in the first half and poor in the second half. We gradually played ourselves into some poor form."
Hull coach Peter Gentle told BBC Radio Humberside:
"We lost Kirk Yeaman early on and all the forwards had to play extended periods.
"We spoke at half time about having players out of position and everyone doing their job - it was a really gutsy win.
I'm still a bit critical of a kicking options but it's all still a work in progress."
FRIDAY NIGHT'S LINE-UPS
St Helens: Wellens; Gardner, Shenton, Meli, Foster; Gaskell, Lomax; Laffranchi, Hohaia, Puletua, Wilkin, Soliola, Clough.
Replacements: Perry, McCarthy-Scarsbrook, Wheeler, Dixon.
Hull: McKinnon; Sharp, Martin, Yeaman, T Briscoe; Horne, Seymour; O'Meley, Houghton, Lynch, Manu, Tickle, Whiting.
Replacements: O'Carroll, Moa, Turner, Ellis.
Referee: Bob Thaler (RFL)