The early goal certainly gave the Perth side a spring in their step. And Celtic's response was predictable. But their failure to get back into this this one was anything but.
In-form Daizen Maeda was the first to have a go, his strike being tipped by goalkeeper Andy Fisher towards the back post when Stephen Duke-McKenna nipped in front of Nicolas Kuhn to make a vital intervention.
Not content with his goal-saving heroics, Duke-McKenna proved a threat up the other end, with his swerving shot pushed past by Celtic goalkeeper Viljami Sinisalo.
The visitors continued to search for the equaliser - Reo Hatate hit a post with a early in the second period and should have done better later on when he blazed over.
At the other end, Benji Kimpioka used his physicality to good effect, as St Johnstone created one or two chances. And Victor Griffith came close to adding a second, his deflected strike looping over.
James Forrest had Celtic's best chance, but his close-range effort was saved by the excellent Fisher, who also kept out an effort by Luke McCowan.
The Perth side held on and their survival bid will continue against Dundee United at Tannadice on Saturday before the post-split fixtures ensue.
St Johnstone will meet Celtic again in their Scottish Cup semi-final on 20 April.