The half time substitute weaved his way past two defenders and then lashed a shot home on 77 minutes, before adding a second to seal the points four minutes from time, curling the ball in direct from a corner.
It had looked for a while like the Yellows would be frustrated, but they maintain their one point advantage at the top over Farsley Celtic, who beat bottom side North Ferriby 4-0.
On a heavy pitch in Cumbria, neither side got off to a particularly good start in a game that was constantly broken up by the referee’s whistle.
Tony Gray steered a header over the bar and Jason Walker curled a shot handsomely wide, before the Yellows came closest on 22 minutes, Bohan Dixon sliding Jack Mackreth down the right and his cross was diverted on to his own crossbar by Josh Calvert perhaps via the fingertips of the ‘keeper.
On the half hour mark, Dixon found himself on the ball with half of the pitch to his left, Alex Whittle created the distraction and it opened up for Dixon to place a shot agonisingly wide of the keeper’s left hand post.
Warrington were forced in to a change at the break as Vassallo came on for an injured Gray, and he proved the match winner.
The closest Workington went was when a clearance was deflected in to the path of Jason Walker, and Tony McMillan was out quickly to smother the chance.
Vassallo showed his potential as the game breaker by winning the ball back on the edge of his own box, travelling up the field and releasing Josh Amis with a perfectly weighted pass, Amis denied by the outstretched leg of ‘keeper Aaran Taylor.
Anxiety grew as the game went in to the final quarter and it took a moment of magic to break the deadlock, Vassallo turning on the ball and weaving through a couple of players, taking the ball in to the box and with plenty waiting for a pull back, he lashed the ball through the legs of Taylor for 1-0.
That gave Warrington a priceless lead to defend, and though Workington pressed forward, they created little in the way of chances.
And the points were safe on 86 minutes when after a corner was won on the right, Vassallo curled it inside the far post direct from the set piece to complete a good night’s work for the league leaders, ahead of Saturday’s trip to Mickleover Sports.
Workington: Taylor, Douglas, Rowntree, Calvert, Smith, Carroll, Holt, Cowperthwaite, Walker, Joel (Thompson), Tinnion (Symington). Unused subs: Brotherston, Maguire, Harker.
Warrington Town: McMillan, Duggan (Evans), Whittle, Beeley, Roberts, Raven, Mackreth (McCarthy), Garrity, Gray (Vassallo), Amis, Dixon. Unused subs: Benjamin, Hughes.