A night of frustration at the University of Bolton Stadium as Wanderers’ unbeaten run came to an end and left them with work still to do to reach the play-offs.
With two games to go, the Whites’ destiny remains in their own hands as they still sit fifth in the table.
But the margin of error was reduced with five points still needed at this stage to guarantee a top-six finish after a first-half goal from Ethan Hamilton gave Stanley the victory they needed to aid their fight against the drop.
Hamilton’s strike kept alive the Reds’ survival hopes and ultimately handed Wanderers a first loss in eight games as Ian Evatt’s men dominated almost throughout but couldn’t repair the damage.
The Whites had chances before and after falling behind to take control of the contest.
But after drawing a blank in front of goal, they must now bounce back against Fleetwood Town on Saturday with their play-off prospects still very much alive.
Wanderers made two changes to their starting line-up as they looked to back up Saturday’s win over Shrewsbury as Declan John and Dan Nlundulu returned to the side.
Nlundulu was busy early on as Wanderers looked to strike a quick blow, although it was Dion Charles who had the first chance against his former club.
Dempsey did well with a typical burst forward before finding Charles, but the striker’s first touch just saw the ball get away from him to give Lukas Jensen the chance to come out and smother.
Stanley were more adventurous than some of the sides to have visited the Unibol in recent times as they looked to get the ball forward and go direct with set-pieces whenever possible.
However, it was from a corner of their own that Wanderers went close again 20 minutes in when a Josh Sheehan effort was blocked and the Whites were then only inches away from taking the lead when Dempsey met a superb cross from John with a flick that flew across the face of goal.
Wanderers increasingly pegged Stanley back as they pushed for the opening goal ahead of half-time but five minutes before the break the visitors struck to grab the lead themselves when Hamilton pounced to beat James Trafford low to his left as the ball dropped just inside the penalty area after Wanderers had conceded possession.
The advantage could have lasted less than 60 seconds but after a flick from Nlundulu had released Sheehan, the midfielder couldn’t beat Jensen for a second goal in two games as the former Wanderers’ loanee spread himself to save and leave Evatt’s men needing a comeback in the second half.
The pattern was set early as Wanderers camped in the visitors’ half but the threat of a counter-attack remained and Stanley almost grabbed a second through former Whites' loan man Hamilton who this time was denied by Trafford as he got down swiftly to make a fine save.
With almost an hour gone Evatt made a double change to try and force the break-through as Shola Shoretire and Cameron Jerome both came on to add something different to the mix.
It was rapidly becoming a game of attack versus defence but despite an effort from George Johnston blocked in front of goal Wanderers couldn’t find the key to unlock the Reds’ back line as the clock began to tick down.
Conor Bradley was a constant threat down the right-hand side and from one of his crosses substitute Elias Kachunga connected with a header Jensen was able to gather.
Jensen was becoming a central figure and after he parried a drive from the tireless Dempsey, Shoretire was thwarted as he tried to follow up.
And with the Reds packing their defence and eating up time wherever they could they managed to keep the Whites at bay.
Evatt utilised every attacking option he could but with referee James Linington allowing only four minutes of added time there was to be no late reprieve with Wanderers now having to take their play-off fight to the wire.
Wanderers: Trafford; Jones, MJ Williams, Johnston; Bradley, Morley, Sheehan, John (Adeboyejo 72); Dempsey; Charles (Kachunga 68), Nlundulu. Substitutes: Lee, Thomason, R Williams, Jerome.
Booked: None
Accrington Stanley: Jensen; Nottingham, Tharme, Rodgers; Clark, Martin, Conneely (Quirk 72), Hamilton, McConville (Longelo 53); Lowe (Whalley 72), Pressley. Substitutes: Savin, Sangare, Nolan, Butler.
Booked: None
Referee: James Linington
Attendance: 17,406 (Accrington 254)