Bournemouth led until the 75th minute when Michael Cummins equalised and then went on to snatch the winner as the Cherries lost their way.
Bournemouth took the lead in the 23rd minute when James Hayter seized on a defensive mistake to set up a simple chance for Andrew Surman to score his fourth goal of the season.
Bournemouth threatened more with Brian Stock forcing a good save from the goalkeeper as Port Vale struggled to contain the home side's eagerness.
But there was a hint of things to come in the 43rd minute when Cummins struck the underside of the Bournemouth bar with his team's first clear chance.
Vale were an improved side after the break but were fortunate not to concede a second goal in the 65th minute when Mark Goodlad made a good save from Surman but the rebound fell into the path of James Keene who shot over from 10 yards with an open goal facing him.
This miss proved to be the turning point of the match because Port Vale took full advantage to draw level and then go on and win.
The equaliser came in the 75th minute when Nathan Lowndes touched the ball into the path of Cummins whose 25-yard shot nestled in the corner beyond the dive of Gareth Stewart.
Cummins went close for Port Vale before the winner came with four minutes remaining.
Chris Birchall centred from the right and Paynter lunged forward to divert a header past Stewart from six yards.
Port Vale had Mickey Bell, Tony Dinning, Sam Collins and Steve Rowland all booked for fouls but it did not detract from their spectacular recovery.
Vale were without midfield player Danny Sonner who limped out of the action after only 10 minutes with an ankle injury.