Scott Laird's close-range strike moved Walsall up to eighth in League One and sent second-bottom Chesterfield a step closer to relegation.
Defender Laird's fourth goal of the season eight minutes into the second half pushed the Saddlers to within six points of the play-offs, while Chesterfield remain eight points adrift of safety.
Only a fine display from veteran stopper Thorsten Stuckmann prevented the Spireites from suffering a heavier defeat.
He spread himself well to stop Isaiah Osbourne poking home from 12 yards after 25 minutes before Chesterfield's best effort saw Kristian Dennis' strike fly straight at Walsall goalkeeper Neil Etheridge.
Stuckmann made another good stop after 37 minutes, a strong one-handed diving save preventing Kieron Morris' 18-yard shot finding the bottom corner after a fine solo run.
The 35-year-old was at it again five minutes later, getting another strong hand to Simeon Jackson's near-post strike after an error from Spireites skipper Ian Evatt.
But Stuckmann was helpless for Walsall's 53rd-minute goal as James O'Connor glanced on Erhun Oztumer's near-post corner and Laird bundled the ball home from close range.
Walsall's sixth straight home victory is their best run at Bescot since winning the first seven games during their promotion-winning campaign under Richard Money in League Two 10 seasons ago.
Match report supplied by the Press Association.
