The Bombers, missing prolific ball-winner Darcy Parish through injury, did it the hard way in their 15.17 (107) to 11.6 (72) triumph at Marvel Stadium on Friday night.
They were left stunned when a 28-point halftime advantage vanished at the start of a see-sawing third term.
The Saints piled on five goals in 14 minutes before the Bombers hit back with the next six majors, including two from Stringer at important stages, to rebuild a match-winning lead.
There was pressure on Stringer after what coach Ben Rutten dubbed a "poor" return from injury the previous week and he had no impact in the first half against St Kilda.
However, the explosive forward provided the spark when needed with 2.1 from nine disposals in the third term to help stave off the Saints' challenge.
"He was back to the Jake that we know," Rutten said.
"He had six tackles and 50-odd pressure points - that's Jake at his best.
"It's not a problem when he gets his hands on the ball, so the (defensive) side of his game is what I was most pleased with."
Essendon's third win of the year snapped a four-match losing streak.
Zach Merrett (25 disposals), Dylan Shiel (25) and Jye Caldwelll (23) won plenty of the ball in Parish's absence and Peter Wright kicked four goals in his 100th game, while Jordan Ridley and Andrew McGrath impressed in defence.
St Kilda star Jade Gresham kicked three goals from 28 disposals and Jack Sinclair (31 disposals) was busy as always, but coach Brett Ratten said Josh Battle was his side's only clear winner.
The Saints (8-5) blew a great chance to move into the top-four amid a hot race for finals spots.
"I think the third quarter probably flattered us a little bit," Ratten said.
"After getting a rocket (at halftime) we came back and showed a bit of fight but by the end of the third it was virtually even again for the quarter.
"That was as hard to watch, for a while, that we've been involved in."
Criticised for a flat start to their 150th anniversary match against Carlton last week, the Bombers turned up the pressure and pounced on St Kilda's early errors.
It led to a 16-point Essendon lead at the first break that would have been greater if not for some wayward shots at goal.
The margin grew to 28 points by halftime as seven different goal-kickers gave the Bombers their second-highest first-half score of the season.
Rowan Marshall and Paddy Ryder kicked the opening two goals of the second half from marks to kick-start the Saints' challenge before Essendon steadied and hung on for a big upset.
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