The 23-year-old led by as many as eight strokes midway through Sunday's final round at Royal Fremantle.
McKinney's momentum stalled somewhat on the back nine, but the triumph was never really in doubt as he carded a three-under 69 for a four-round total of 270.
Former Australian Open runner-up Curtis Luck (67) and fellow Australians Kirsten Rudgeley (68) and Abbie Teasdale (70) tied for second at 274 in the event where men and women play alongside each other off different tees for the same prize money pool.
English crowd favourite Andrew "Beef" Johnston had a dirty day with the putter and finished in a tie for sixth at 277 after a final round of two-over 74.
The Scottish-born McKinney will ply his trade on the DP World Tour in 2026 after successfully negotiating all three stages of qualifying school late last year.
He also won the Australian Amateur title in 2022.
McKinney entered the final day with a three-shot buffer after a red-hot finish to Saturday's third round, which included a hole-in-one on the par-3 17th and a birdie on the 18th.
He began Sunday's round in similar fashion with a birdie and an eagle on the first two holes.
McKinney led by as many as eight shots after yet another birdie at the 8th hole got him to 21 under.
He had three bogeys on the back nine, but by then the title was his for the taking.
11°C