Birstall will meet holders Methley in the Jack Hampshire Trophy final after a thrilling five-run victory over Townville in the semi-final on Sunday.
Craig Wood (103) and Rob McFarlane (111 not out) produced a brilliant batting display to propel the visitors to a close on 263-2.
In reply, Townville’s Jonathan Booth (76), Tim Walton (54) and Ray Bresnan (56) all stood firm, as Danny Broadbent (5-51) applied the pressure, to set up a thrilling finish.
The game went down to the final ball but Townville failed to score a six from the final ball that would have given them victory.
In the other semi-final Methley defeated Wrenthorpe by six wickets.