A second try from in-form centre Shontayne Hape - his 12th in nine games - three minutes from the end settled a pulsating final eliminator and condemned Saints to a third successive home defeat for the first time in eight years.
However, Saints can hold their heads high after pushing the in-form Bulls all the way in a titanic battle at Knowsley Road.
Shorn of Sean Long, Paul Sculthorpe, Darren Albert, Mark Edmondson and Jason Hooper through injury, Saints had 17-year-old Scott Moore making only his seventh senior appearance.
And the signs were ominous as Bradford, in buoyant mood after 10 straight wins, raced into a 12-0 lead after 12 minutes.
Winger Ade Gardner led Saints out on his 100th appearance before settling down to mark danger man Lesley Vainikolo and they made the perfect start, forcing the Bulls to concede a 10-metre scrum from the kick-off.
But Bradford�s defence held firm and Hape, the man bundled into touch on the first tackle of the match, made amends with the opening try after three minutes, crossing wide out after Brad Meyers had been stopped by full-back Paul Wellens.
Paul Deacon added the conversion, with the aid of a ricochet off the right upright, and after he maintained the pressure with a 40-20 kick, Bradford added a second try on 12 minutes when second rower Paul Johnson took Stuart Fielden�s offload to ghost through the home defence.
Deacon�s second goal made it 12-0 but the Bulls missed further glorious opportunities when Meyers and Jamie Langley knocked on to ruin potential overlaps and they were as guilty as their opponents in frittering away possession.
Saints needed no second invitation as they struck back with a brace of tries from Wilkin in an eight-minute spell midway through the first half.
The former Hull KR back-row forward took an inside pass from skipper Keiron Cunningham to grab his first on 19 minutes and then was on hand to cross again after winger Ian Hardman had palmed back Jamie Lyon�s crossfield kick.
Lyon added both conversions to tie the scores and put over a penalty six minutes before the interval to edge his side in front for the first time.
There was no let-up in the intensity in the second half as the lead changed hands twice more within 10 minutes of the restart.
Bradford regained the advantage when substitute Jamie Langley made amends for his earlier clanger when he took the ball from Deacon and tore away from his pursuers to crash over at the corner.
Deacon was off-target for the first time and Saints were back in front within seven minutes when Wilkin completed his hat-trick, forcing his way over from dummy-half after Willie Talau had been held short.
This time Lyon lost his 100% record and the scores were deadlocked once more on 54 minutes when Deacon put over a penalty awarded for a high tackle by Nick Fozzard on Morley.
The deadlock was broken by a 30-metre drop goal from Deacon 10 minutes from the end but the frenzied action continued right to the final whistle.
Moore and Mick Higham both knocked on in promising positions and Wellens was tackled agonisingly short of the line, while Langley spilled another pass when a try was there for the taking.
But the clincher came when Iestyn Harris sent out a long pass to the left where Hape just had enough room to cross for his second, and most important, try of the night.
St Helens: Wellens, Hardman, Lyon, Talau, Gardner, Wilkin, Moore, Fozzard, Cunningham, P. Anderson, Gilmour, Bennett, V. Anderson. Replacements: Higham, Roby, Fa'asavalu, Graham.
Bradford: Withers, L. Pryce, B. Harris, Hape, Vainikolo, I. Harris, Deacon, Peacock, Henderson, Fielden, Johnson, Meyers, Radford. Replacements: Paul, Langley, Morley, Vagana.
St Helens: (14) 18. Tries: Wilkin 3. Goals: Lyon 3.
Bradford: (12) 23. Tries: Hape 2, Johnson, Langley. Goals: Deacon 3. Drop Goals: Deacon.
Referee: Karl Kirkpatrick (Warrington) Att: 11,604
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Thanks to www.superleague.co.uk for this report.