A fine free-kick from Darren Wrack deep into second-half stoppage time saved Walsall's blushes as Barnsley looked certain to collect their first away win of the season.
The free-kick was given for a foul on teenage substitute Leroy Williams about 20 yards out and Wrack curled a great shot into the net off the right-hand post of Barnsley keeper Nick Colgan.
It was unlucky for The Tykes who had looked the better side for much of an ordinary game.
Barnsley took the lead in the 16th minute when a corner by Stephen McPhail was flicked on by former Walsall defender Matt Carbon for Barnsley skipper Tony Vaughan to score with a free header.
Wrack missed a great chance for Walsall six minutes later, but Barnsley looked the better side and the Saddlers' defence was exposed again in the 25th minute when a cross by Chris Shuker was headed wide by the unmarked Mick Boulding.
Barry Conlon and Boulding were causing all sorts of problems for Walsall up front, but Barnsley suffered a blow in the 34th minute when the injured McPhail had to be replaced by Nicky Wroe.
Walsall equalised just two minutes later through Matt Fryatt with his fourth goal of the season.
The youngster scored from close range when Wrack flicked the ball on following a pass by Jorge Leitao.
Barnsley continued to look the better side and regained the lead four minutes after the interval when Conlon earned his just rewards for a hard working display by scoring another free header from a cross by Tom Williams.
Walsall keeper Mark Paston saved from Carbon in the 53rd minute and at the other end a header by Walsall's Neil Emblen was cleared of the line.
Barnsley were easily the more dangerous and Paul Reid walked through the Walsall defence only to shoot wide in the 73rd minute.
A minute later Boulding had yet another free header from Shuker's cross, but Paston saved.
Wrack had an effort cleared of the line as Walsall looked for a way through the well organised Barnsley defence, but the midfielder finally got the equaliser in the dying seconds.