Ko finished at 13-under 275 at The Vancouver Golf Club, pulling away with birdies on five of the first six holes on the back nine.
Lydia Ko won the Canadian Women's Open on Sunday to become the youngest winner in LPGA Tour history and only the fifth amateur champion.
The 15-year-old South Korean-born New Zealander closed with a 5-under 67 for a three-stroke victory. She broke the age record of 16 set by Lexi Thompson last September in the Navistar LPGA Classic in Alabama, and is the first amateur winner since JoAnne Carner in the 1969 Burdine's Invitational.
In January, Ko won the New South Wales Open in Australia at 14 to become the youngest player to win a professional tour event, a mark broken by 14-year-old Brooke Henderson in June in a Canadian Women's Tour event in Quebec. Ko also won the U.S. Women's Amateur two weeks ago in Cleveland.
Ko finished at 13-under 275 at The Vancouver Golf Club, pulling away with birdies on five of the first six holes on the back nine. She opened with consecutive 68s and shot a 72 on Saturday to take a one-stroke lead into the final round.
Inbee Park shot a 69 to finish second.
U.S. Women's Open champion Na Yeon Choi, Chella Choi and Jiyai Shin tied for third at 8 under. Na Yeon Shoi had a 73, and Chella Choi and Shin shot 71.