Stoke loanee Julien Ngoy scored just four minutes after coming on for his debut as the Saddlers beat struggling MK Dons.
The striker, signed at 10:59pm on loan from Stoke on transfer deadline day, took down a long ball before firing home at the near post with 20 minutes remaining.
The result moves Walsall up a place to 16th in League One, four points clear of the relegation zone.
The Saddlers started in determined mood, registering three efforts inside the opening four minutes.
Joe Edwards first saw a 25-yard drive parried by visiting keeper Lee Nicholls before Amadou Bakayoko fired over.
Erhun Oztumer then twisted and turned on the edge of the box before lashing a left-footed shot wide.
The hosts were dominant and could have been awarded a penalty when Adam Chambers went down under a challenge from Alex Gilbey – but referee Christopher Sarginson waved play on.
Bakayoko then volleyed wide as MK continued to cause themselves problems by trying to play out from the back.
The final 20 minutes of the first half was a scrappy affair, with Walsall not threatening again until just before half-time when Oztumer looped a header wide from Edwards’ cross.
After being comfortably second best in the first half, Dan Micciche’s Dons improved considerably after the break.
Kieran Agard fired a 20-yard strike inches wide, Robbie Muirhead lashed a blistering effort off target and Agard curled a right-footed shot just beyond the far post.
The Saddlers should have taken the lead on 62 minutes when Edwards’ blocked shot fell to Bakayoko but, leaning back, the striker blazed over from close range.
A minute later, Walsall’s Jon Guthrie had to be in the right place to clear Muirhead’s hooked effort off the line after keeper Liam Roberts had failed to claim a cross.
Boss Jon Whitney made a double substitution on 66 minutes, bringing on Justin Shaibu and Ngoy for Bakayoko and Oztumer.
The change paid instant dividends as Ngoy put Walsall ahead just moments later, cutting inside onto his right foot and arrowing a low shot past Nicholls at his near post.
The visitors almost responded immediately but Roberts reacted well to parry Ed Upson's powerful strike from inside the area.
MK applied some pressure late on but it was the Saddlers who went closest as Ngoy shot wide on the turn.
Team: L Roberts, Kinsella, Fitzwater, Guthrie, Leahy, Chambers, Edwards, Dobson, Oztumer (Ngoy 65’), Morris, Bakayoko (Shaibu 65’).
Subs not used: Gillespie, K Roberts, Cuvelier, Flanagan, Kouhyar.
Attendance: 4,009 (436 MK Dons supporters).