Second best on a testing afternoon in which the hosts could rightly claim to be unfortunate not to triumph and claim three precious survival points, Barnsley were on the cusp on recording a fifth draw in seven matches and a third successive goalless draw, only for the returning Brown to net at the death.
It was harsh on a dominant Walsall, with their best moment coming in the second half when only a remarkable goalline clearance from Ben Williams denied Josh Gordon.
Jack Walton, starting in goal with Adam Daives on international duty with Wales, also made a key save to deny the same player on the restart.
The game was also notable for Barnsley recording their seventh successive league clean sheet for the first time since April 1955.
Walsall may have headed into the game on the back of a poor run of seven defeats in their previous nine league outings, but looked nothing like a side in the bottom four on the evidence of the first half.
The Saddlers showed tenacity, enthusiasm and drive, with Zeli Ismail causing problems in particular down the right, with the speed of their front free posing problems on the break.
Errant finishing proved the hosts’ bugbear with Gordon wayward after being played in by Corey Blackett-Taylor and Liam Kinsella also producing a high and wild finish when well placed after latching onto a dangerous low centre from Ismail, who tested Ben Williams throughout the first period.
At the other end, Barnsley were rather inhibited with their best chance coming on 36 minutes with Mamadou Thiam saw his snapshot parried alertly by Liam Roberts.
it was a half which also saw the Saddlers find the net early on, only for referee Ben Toner to blow for a free-kick shortly before Isaiah Osbourne lashed home a thunderous volley - with Gordon penalised for an earlier foul.
Walsall carried on from where they left off in a vibrant first half on the resumption with a fizzing drive from impressive captain George Dobson flying over, with Barnsley struggling to assert themselves at the other end.
One half-chance ended with Mike Bahre steering an effort over, with Barnsley lacking a touch of composure on an admittedly tricky surface.
After an accomplished performance, Walsall cranked up the gas with a strong spell just pastr the hour mark and went extremely close to an opener on two occassions.
Brilliance on the goalline from Ben Williams denied Blackett-Taylor before a shot from Ismail was deflected just wide as the hosts went for the jugular.
In a bid to wrestle back control, Callum Styles was brought onto stiffen central midfield, with Bahre being the man to make way.
But it was Walsall who continued to dominate with Walton doing superbly to deny Gordon, before the same player was thwarted by another last-ditch challenge as the hosts laid siege.
The opportunity that the Reds craved then arrived 11 minutes from time, but Liam Roberts made a fine point-blank save to block Woodrow’s goalbound effort.
But there was no stopping Brown in stoppage time, when he netted following late pressure.
Walsall: L Roberts; Devlin, Scarr, Guthrie, Leahy; Kinsella, Dobson, Osbourne; Ismail (Ferrier 89), Gordon, Blackett-Taylor. Substitutes unused: Dunn, Edwards, Cook, Fitzwater, Laird, Oteh.
Barnsley: Walton; Cavare, Pinnock, Lindsay, B Williams; McGeehan (Adeboyejo 76), Mowatt; Brown, Bahre (Styles 68), Thiam (Green 84); Woodrow. Substitutes unused: Greatorex, Fryers, Jackson, J Williams.
Referee: B Toner (Lancashire).