Substitute Fletcher powered in a header from Simon Francis’ perfect cross in the third minute of stoppage time, just when the Saddlers thought they had done enough to win.
A rash challenge by Walsall defender Lee Beevers on Marc Pugh had handed the Cherries a 62nd-minute penalty, which brought them back into the game, Michael Symes smashing home the spot-kick.
Walsall were all over Bournemouth in the first half and deserved their two-goal interval lead. They had an anxious moment in the 12th minute when veteran goalkeeper James Walker, equalling a club record with his 529th appearance, was shown just a yellow card for handling while on the floor outside his area.
However, the Saddlers took the lead three minutes later when the outstanding Richard Taundry delivered a low cross to the feet of Jon Macken who swivelled to drill home his sixth goal of the season.
And a minute before half-time, Walsall skipper Andy Butler added a second when Taundry’s corner was driven into the goalmouth by Alex Nicholls, blocked on he line, and the defender headed in the rebound.