With the game seemingly headed towards a goalless draw, Danny Johnson fired the Saddlers in front with just a minute of normal time remaining.
But, remarkably, Danilo Orsi snatched a point for the Red Devils in the 95th minute, sparking pandemonium among the 77 travelling Crawley fans.
The results leaves the Reds 12th in League Two going into Saturday’s trip to second-from-bottom Forest Green Rovers.
Scott Lindsey made two changes from Saturday’s home defeat to Crewe Alexandra.
Dion Conroy was forced out through injury and replaced by Travis Johnson. The other change saw Kellan Gordon replace Aaron Henry.
The Reds enjoyed the best of a first half short of clear-cut chances. The visitors saw the ball scooped off the Walsall goal-line and Ronan Darcy drag an effort wide from the edge of the box inside the opening ten minutes.
Darcy and Klaidi Lolos both saw shots blocked but neither side could break the deadlock before half-time.
But if Crawley had the better of the first half, Walsall had the better of the second.
Crawley goalkeeper Corey Addai made three saves in five minutes, denying ex-Reds loanee Isaac Hutchinson twice before keeping out Tom Knowles’ half-volley.
The Saddlers then had two further chances in quick succession. Donervon Daniels was denied a superb goal by Addai before Hutchinson fired an effort just inches over the bar.
Johnson was then kept out by Addai from point-blank range as Walsall continued to crank up the pressure.
The Reds had their first attempt of the second half on 77 minutes, but Laurence Maguire’s headers was straight at Saddlers stopper Owen Evans.
Walsall eventually found their opener with a minute to go. Brandon Comley's shot hits the post but Johnson was on hand to knock the rebound into an empty net.
But the Reds weren’t to be undone. Orsi poked the ball over Evans following a free-kick to salvage a point for Crawley in the last minute of added time.
Crawley Town: Addai, Wright, Johnson, Maguire, Williams, Gordon, Darcy (Khaleel 75), Kelly, Tsaroulla, Lolos (Roles 85), Orsi.
Unused: Ashby-Hammond, Omole, Forster, Henry, Swyer.
Attendance: 4,108 (77 away)