The Yorkshire side took the direct route to the Northern Ford Premiership Grand Final on the strength of a kicking game that has surely not been bettered in either division this season.
Richard Agar was the man largely responsible, exploiting the 40-20 rule with ruthless efficiency and also landing three of the League leaders' four drop goals.
His first contribution was with his hands, however, supplying the pass for Nathan Graham to score the game's first try after four minutes. Mark Hewitt reduced the deficit with a penalty, but after that Widnes were kicked to death by Agar and co.
A series of touch-finders giving Dewsbury possession from the scrums produced drop goals from Agar and his half-back partner, Barry Eaton, before their Australian centres linked for Paul Evans to send Brendan O'Meara over.
Two goals from Eaton put the Rams firmly in control and the game was effectively won when Agar put over his second drop goal soon after the break. Graham's pass sent Damian Ball in for another try before a lovely long ball from Agar released Andrew Spink.
Agar, a candidate for the Player of the Year award in the Premiership, slotted over his third drop goal before O'Meara and Widnes's Paul Hulme went to the sin-bin for fighting, something that seemed to trigger a brief skirmish on the terraces as well.
Dewsbury kept their minds on the job, with Sean Richardson setting up Ball for their final points. A well-beaten Widnes managed just a token effort in the last minute from Paul Mansson.
They must now beat Hunslet next Sunday to earn another crack at Dewsbury in the Grand Final at Headingley on 25 September and there is still an argument that they are determined to pursue with the League over who should have home advantage next weekend.
Dewsbury looked the best-organised side in the competition by a distance. What they lack is what Widnes have got - a ground that meets Super League specifications.
Dewsbury: Graham; Godfrey, Evans, O'Meara, Flynn; Agar, Eaton; Boothroyd, Delaney, Long, Spink, Haigh, Ball. Substitutes used: Richardson, Medley, Hicks, Jowitt.
Widnes: Munro; P Smith, Percival, Hassan; Verbickas, Mansson; Hewitt, Hansen, Cantillon, Savelio, Mann, Adams, Hulme. Substitutes used: Briers, D Smith, Devecchi, Mill.
Referee: S Presley (Castleford).Reuse content