The Rams fully deserved to lead 17-4 entering the final 15 minutes but Toronto struck with a quickfire three-try blast to break Rams hearts.
The Rams had been more than a match for big spending full-time outfit Toronto and had the Canadian franchise rattled as they threatened to inflict a first defeat of the campaign on the Wolfpack.
Paul Sykes capitaised on poor Toronto discipline to kick five penalty goals, while his 63rd minute drop goal had put the Rams into a 13-point lead.
Sykes edged the Rams ahead with a seventh minute penalty and repeated the feat soon after to make it 4-0.
Dewsbury had Toronto on the back foot and Adam Ryder stormed towards the line to set up another attack before Kyle Trout’s powerful drive saw him over the line between the posts but he was unable to get the ball down under a cluster of defenders.
From the last tackle, Sykes produced a neat inside kick between the posts and Michael Knowles managed to get a hand on the ball before it rolled dead, with Sykes converting to put the Rams in control.
A terrific kick and chase by Dewsbury again put Toronto under pressure as they knocked on and the Rams forced a repeat set when the visitors scooped a dangerous kick dead.
Toronto were penalised again but Sykes was narrowly off target with another shot at goal.
Dewsbury cut loose again shortly after when Rob Worrincy made a terrific break but held onto the ball with Sykes well placed on his inside.
Sam Day, Trout and Chris Annakin all linked and when the ball was kicked in goal, Luke Hooley just failed to ground it as Toronto continued to be forced onto the back foot.
The Wolfpack had failed to mount an attack of note in the opening half hour but eventually hit back as they moved play right and winger Adam Higson dived over in the corner but Gareth O’Brien was well wide with his conversion attempt.
Knowles clattered the left post with a drop goal attempt in the final minute of the first half but the Rams left the field to a standing ovation by the home fans, who sensed a shock was on the cards.
Terrific Rams defence denied Toronto from an early second half attack and when the Rams moved back downfield, Sykes slotted over his fifth goal after the Wolfpack had been penalised for interference at the play the ball.
Moments later, Toronto were put on a team warning after conceding another penalty and Sykes was again on target to stretch the lead.
Toronto could count themselves fortunate not to have a man sin-binned when Worrincy appeared to be tipped up in a tackle but after Dewsbury took play into the Wolfpack 25, Sykes slotted over a drop goal as the Rams led 17-4.
Toronto then hit back in the 67th minute when a kick through by Josh McCrone was pounced by Ryan Breirley - who was a late replacement in the Wolfpack side after Bodene Thompson pulled out in the pre-match warm-up - and O’Brien converted.
Dewsbury sent the kick off out on the full and Toronto attacked again from the resulting penalty, with Blake Wallace forcing his way over, twisting in a tackle to plant the ball down, with O’Brien’s conversion reducing the deficit to a single point.
Toronto then struck the killer blow with a third try in the space of just five minutes as they opened the Rams defence up on the right and O’Brien scooted through a gap to cross for the try, which he improved.
There was drama in the final five minutes as Darcy Lussick was sin-binned for a high tackle, which sparked a brawl, but Dewsbury’s Dan Igbinedion was also shown a yellow card for retaliation.
Dewsbury were on attack from the resulting penalty when a touchjudge intervened having spotted an incident in back play and referee Michael Mannifield showed Annakin a straight red card as the Rams ended with 11 men.
Dewsbury tried valiantly to force a last gasp attack but it wasn’t to be and Toronto breathed a huge sigh of relief at the final hooter.
Dewsbury Rams: Hooley; Worrincy, Walshaw, Ryder, Morton; Sykes, Knowles; Annakin, Day, Garratt, Kibula, Harrison, Trout. Subs: Ward, Igbinedion, Field, Andrade.
Toronto Wolfpack: O’Brien; Higson, Rawsthorne, Leutele, Russell; Wallace, McCrone; Sidlow, Ackers, Lussick, Dixon, Olbison, Wilkin. Subs: Beswick, Mullally, Brierley, Springer.
Referee: Michael Mannifield.