But coach Richard Marshall was left with plenty to think about after the Rams led 6-0 until the final play of an uninspiring first half.
Halifax raised the bar after the break, scoring five tries to nil to cement a crucial success.
Halifax started smartly, rolling forward down the middle and restricting the Rams’ progress with the ball. But once those initial exchanges were over, the contest gradually deteriorated, with both error and penalty counts, the latter finishing 13-11, rising steeply.
It was the Rams who summoned enough guile to take the lead, half back Dominic Speakman stabbing in a short kick at the line and regathering to score from close range.
Paul Sykes added the conversion and that was it for scoring for the next half hour.
On the stroke of half time, the home side finally conjured a response, full back Will Sharp firing out a long pass to James Saltonstall and the winger finishing athletically by the flag.
Steve Tyrer levelled the half time scores with the touchline conversion, setting the stage for a largely one-sided second period.
Halifax emerged energised and perhaps chastised, scoring almost immediately through the impressive Simon Grix and then adding a classic Rob Worrincy touchdown with 24 minutes remaining.
With Tyrer converting the latter, that pushed the scoreline out to 16-6, a deficit that already looked too much for the Rams to close. Tyrer followed up with two final quarter tries, both converted, before Adam Tangata rounded off a win that was numerically comfortable, but hardly convincing.
Halifax: Sharp, Saltonstall, Tyrer, Heaton, Worrincy; Murrell, Johnston; Tangata, Kaye, Cahalane, Grady, Grix, Fairbank. Subs: Lannon, Morris, Moore, Boyle
Dewsbury: Guzdek; Brown, Sykes, Gibson, Morton; Brown, Speakman; Walker, Ward, Douglas, Walshaw, Spicer, Annakin. Subs: Hemingway, Ollett, Batchelor, Tonks
Referee: S. Mikalauskas