Paul Hanlon and Eoin Doyle were on target as Hibs made it back-to-back wins in the Scottish Premier League.
The home side rarely threatened in the first half but a header from Hanlon looped over St Johnstone keeper Alan Mannus on the stroke of half-time.
Doyle knocked in a 53rd-minute rebound from six yards after Mannus had stopped his initial effort.
With Hibs growing in confidence, St Johnstone fell out of the game and could not find a way back.
Pat Fenlon's side were far from their best in the opening 45 minutes but there is a new-found steel to the men in green, who move up to second in the table on seven points.
The visitors welcomed back striker Rowan Vine and Gregory Tade from suspensions and had Hibs pinned back for most of the first half.
With central midfield duo Gary Deegan and Jorge Claros sitting deep, the home side were very slow out of the blocks and could not service in-form striker Leigh Griffiths, who had scored twice in last weekend's success at St Mirren.
Hanlon made a good sliding block in front of his own goal as Liam Craig fired in a low shot after his free kick was blocked by the defensive wall.
St Johnstone's Nigel Hasselbaink then fluffed his shot after a positive burst into the penalty area, allowing Hanlon to clear again.
Deegan was caught dithering in possession and was relieved to see defender James McPake recover the situation by ushering the powerful Tade away from goal.
The Hibs captain again thwarted the St Johnstone striker when Tade came charging in from the left only to take a clumsy touch which gave McPake the opportunity to make an excellent sliding tackle.
St Johnstone full-back Dave MacKay fired wide from 30 yards and Hasselbaink should have done better when he over-hit a cross for the unmarked Vine at the back post.
With the Perth continuing to press, Murray Davidson cleverly steered the ball towards Vine with his chest but the striker's shot from the edge of the penalty box was smothered by Hibs keeper Ben Williams.
Completely against the run of play, Hibs snatched the lead when Hanlon rose to meet a Griffiths corner on 45 minutes.
The defender's header smacked down into turf and bounced over Mannus and had clearly crossed line by the time Callum Davidson had executed an acrobatic clearance.
The second half opened with Paul Cairney jinking into the penalty area but Steven Anderson made a great lunging block just as the Hibs midfielder was about to pull the trigger.
Hibs doubled their lead when Doyle knocked in his first goal of the season from close range.
Griffiths did well to race in from the left and pick out his strike partner with a low cross and while Mannus made a great save to keep out Doyle's first shot the Saints keeper could do nothing about the follow-up effort.
Tade had a great chance to reduce the deficit when McPake was caught out by a long ball over the top but Williams was out swiftly to make an impressive sprawling save near the penalty spot.
At the other end, McPake headed narrowly wide of the target after throwing himself at a David Wotherspoon corner.
Hibs worked the ball from one penalty box to the other with some neat passing which culminated with Mannus saving comfortably from Cairney's cute dink.
The same player then saw a shot blocked by a blue-shirted defender as the ball broke his way from a corner.
St Johnstone faded as an attacking force as Hibs improved their passing game, although Craig did lash in a dipping shot from 20 yards that Williams was equal to.
And the impressive Williams was right behind a header from Saints substitute Peter Pawlett in the closing minutes.
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