Wheatley full-back Ed Squires' excellent display was the difference between the teams. Castleford's good display was undone by a poor tactical decision in the closing stages.
The first half hour of an entertaining game was end-to-end, with both defences holding firm.
Wheatley were gifted the lead from a seemingly harmless kick by Squires. His opposite number Paul Philpott, struggling to catch the ball, could only kick it forward on the full.
It rebounded off a player and when Danny Price failed to scoop up the loose ball, Squires was on hand to score under the posts. Dan Storey goaled for a 7-0 lead.
An Ian Mattison penalty from 30 metres cut the gap and though both sides pressed late in the half, it remained 3-7 at the break.
The visitors produced the move of the match to score the opening points of the second half. Squires, spotting a bunched defence, asked for quick ball and joined the line to go over unopposed, with Storey again adding the extras.
Wheatley came under pressure and lost a man to the sin-bin for handling on the floor. Cas took advantage when, following a series of drives, centre John Bramham broke through to put winger Martyn Dye in at the corner.
Wheatley had a second play sin-binned and Cas piled on the pressure. It led to three five-metre line-outs before super-sub Bradley Christian powered under the posts. Mattison's conversion gave the home team a 15-14 lead with ten minutes left.
The Cas pack were still on top but from a scrum on their own ten-metre line they decided to run slow scrum ball.
In a man-and-ball tackle, the ball went loose and was hacked forward and despite the attention of prop Gareth Paul, Wheatley worked a try for winger Jamie Webb under the posts. Storey's conversion settled the outcome.
Castleford visit Old Brodleians on Saturday in an EDF Senior Vase third round clash.