The 18-year-old retained the Race to the CME Globe title -- given to the golfer who wins the most points during the LPGA Tour season -- to pick up her bumper prize.
Ko finished joint seventh at the season-ending CME Group Tour Championship in Italy.
"It's been a long season of ups and downs as well, mainly ups, but I think every emotion went through me today," said Ko, who was reduced to tears during an emotional final round.
"What triggered the tears more is what a tough day it was.
"I tried to stay patient all day and even up to the last minute I had a putt lip out, so it was tough, but it's been a long season. I think the hole was smaller than the ball today.
"I'm happy that the season is over and I can relax now."
South Korean Inbee Park and American Lexi Thompson could have both finished above Ko, but missed birdie putts on the penultimate hole to hand the New Zealander top spot.
Thompson's compatriot Cristie Kerr won the tournament by one stroke after finishing on 17 under par -- six shots ahead of Ko. The 38-year-old pocketed $500,000 to move past $17 million in career prize money.
On top of her CME Globe title success, Ko also picked up the LPGA Player of the Year award, becoming the youngest player in its 49-year history to do so.
In September, she won her first major title at the Evian Championship in France, and October's victory at the co-sanctioned Taiwan event was her fifth success this season.
"At the start of the week, I would say the biggest trophy that would mean a lot to me would be the Rolex Player of the Year," Ko told LPGA.com
"I'm so thankful to my team. I'm still emotional."