Requiring 198 to make NSW bat again, The Warriors put the shutters up from the opening over of the fourth day, but fell short of salvaging a draw as they were eventually bowled out for 147 after tea.
Bancroft almost single-handedly saved WA, displaying incredible powers of concentration in scoring 86 off 263 balls in a five-hour innings.
It followed a seven-hour 138 not out in the first innings as Bancroft carried his bat in a total of 279.
Bancroft fell just 28 balls short of breaking Steve Waugh’s all-time Shield record for the most deliveries faced in a game, the former Test captain’s mark of 649 set in 1996 against Queensland still the most in the Shield’s history.
The 26-year-old's tally of 621 is the fourth-most in Shield cricket and he also broke his own Western Australian record of 567 set against NSW at the WACA in 2015.
He's the only man to have faced more than 550 balls in a Shield match twice.
Bancroft was finally out for the first time in the match to be the seventh wicket to fall, with the home side wrapping up the contest shortly after.
WA batted for 91.2 overs in their second innings with Josh Inglis (22 off 83 balls) and Hilton Cartwright (11 off 76) doing their best to support Bancroft.
The Warriors are back in action on Sunday, when they host South Australia at the WACA Ground in their RD 8 Sheffield Shield clash.
