Trevor Benjamin scored a late winner to ensure Walsall secured automatic promotion to League One and put a huge dent in Notts County's play-off hopes.
Defeat was harsh on the home side who dominated throughout and hit a post early on through James Walker's drive.
Kevin Harper's stunning 25-yard strike handed Walsall the lead, before James Dudfield levelled from close range.
County defender Stephen Hunt then had an effort cleared off the line before Benjamin won it with a firm shot.
Notts County: Pilkington, Pipe, Edwards, Hunt, McCann, Silk (Ross 59), Somner (Weston 74), Smith, Dudfield, Lee, Walker (Parkinson 66).
Subs Not Used: N'Toya, Byron.
Goals: Dudfield 41.
Walsall: Ince, Pead (Smith 73), Gerrard (Taylor 46), Westwood, Fox, Harper, Dobson, Keates, Cooper (Wrack 46), Butler, Benjamin.
Subs Not Used: Bossu, Sam.
Goals: Harper 17, Benjamin 84.
Ref: K Friend (Leicestershire).