Defender Chris Westwood grabbed the crucial goal, popping up to head home Mark Kinsella's cross in the 62nd minute. But no less vital to the Saddlers' cause had been a brilliant save by goalkeeper Clayton Ince a minute before the goal to foil Hereford's Tim Sills.
Walsall had the better of the first period but patient build-ups were often spoiled by a misplaced final pass.
The Saddlers' Trinidadian striker Hector Sam was the first to fire in a shot, sending his effort wide of the Hereford goal from 20 yards.
Later in the half United goalkeeper Wayne Brown comfortably held a Michael Dobson shot and then watched as Dean Keates' 20-yard drive fizzed narrowly wide of the target.
At the other end, Ince had a relatively untroubled time as well. The keeper calmly gathered a couple of Hereford corners but his only serious moment of anxiety in the half came on 38 minutes.
Ince came off his line to try and catch a Neil MacKenzie free-kick but Bulls skipper Tamika Mkandawire got there before him and headed the ball goalwards, only for a defender's boot to hammer the ball to safety.
Just before the interval Walsall suffered a blow when midfielder Darren Wrack had to leave the field to be replaced by Mark Wright.
Ten minutes into the second period, a fine tackle by Phil Gulliver foiled Mark Butler as Walsall made the early running. But an Alex Jeannin cross picked out Tim Sills at the other end and the big striker's header seemed to be heading for the corner before Ince got a vital touch.
Almost immediately, Walsall forced a corner as Dean Beckwith got in a fine challenge on Butler.
Kinsella's corner kick was cleared but the Republic of Ireland international returned the ball to the centre for Westwood to head home.
Andy Williams volleyed wide and Ince saved comfortably from Mkandawire's header in the dying minutes but otherwise the Saddlers had few alarms as they held on for their 12th win of the season.