Saints substitute Nathan Lowndes pounced with just seconds remaining to steal a point and scupper Aberdeen's hopes of claiming a top-six SPL place.
It looked like Aberdeen had captured maximum points when Derek Young drilled home a 73rd minute goal.
But St Johnstone dug in and showed a measure of character that has been sadly missing from their play in recent months.
The outcome was a further blow to Aberdeen, whose chief executive Dave Cormack and director Jim Cummings resigned their posts earlier in the day.
The game started in bright enough fashion, with the Perth team setting the pace.
Striker Paul Hartley, so often a fringe player at McDiarmid Park, shot narrowly wide in the fourth minute following intelligent play by Tommy Lovenkrands and Keigan Parker.
Parker must have thought he had opened the scoring a minute later when Ryan Esson fumbled his shot - but the Aberdeen defence managed to clear before Hartley could intervene.
In the 17th minute Hartley twisted past Jamie McAllister on the edge of the area but his raking right-footed shot was well tipped away by Essen.
Saints took the lead in the 25th minute when Hartley delivered a wonderful 40-yard angled cross which McBride headed in from six yards.
Aberdeen, despite their sluggishness, managed to equalise on the half hour mark, when Saints' Stuart McCluskey could only deflect Darren Young's 18-yard shot past his own goalkeeper Alan Main.
Five minutes later Aberdeen went in front. Winters showed his alertness when taking advantage of slack play from McBride on the edge of the area before clipping a lovely finish off Main from close in.
The second half for long periods was a miserable affair - but out of nothing McBride slammed his second goal of the game to tie the scores.
Within a minute the home support were celebrating what they hoped would be the game's winning goal.
But their celebrations were short-lived. Lowndes, who had replaced Hartley in the latter stages, reacted first in a goalmouth scramble to prod the ball past Essen from close range and grab a point for the Perth side.