A Jon Clarke-inspired performance put Widnes in control after the veteran hooker had a hand in two of the Vikings' first-half tries which gave them the platform for victory.
The home side, who have been rooted to the foot of the ladder for the majority of the season, got off to a blistering start thanks to Stefan Marsh, one of eight former Wigan players in the Widnes line-up, after he latched on to a Cameron Phelps' pass.
Nick Youngquest replied for the Tigers, who played without a recognised pivot for 30 minutes until skipper Danny Orr showed up from the bench.
Castleford's lacklustre attacks were few and far between - clearly missing star player Rangi Chase who remains absent due to internal disciplinary reasons. They did muster one decent bit of play towards the close of the first half through Jordan Thompson but the centre could not collect a regulation pass deep in Widnes territory.
Widnes' grip on the game continued as blockbusting second-rower Frank Winterstein barged his way over from close range in the 22nd minute before Ben Davies added a third try just before half-time.
Pat Ah Van's three conversions, all easily kickable, went over and the game was Widnes' to lose entering the second period with an 18-4 lead.
Ian Millward, the Tigers boss, must have given his troops an ear bashing at the break as the visitors came out more fired up but it did not last for long as Paul McShane crashed over from the dummy half for a converted try and then Joe Mellor flew over after a neat show and go.
Ah Van missed his first conversion of the evening but it mattered little in the grand scheme of things.
Stuart Jones got a score back for the sorry Tigers, Craig Huby tagging on the extras but Widnes were soon restoring their lead with another try, this time through debutant Eamon O'Carroll who pounced on McShane's dab through. Ah Van then flew in for a try himself at the end with Rhys Hanbury slotting the goal from the touchline to round things off.
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