Jorge Parada confirmed to NZME that he is no longer the swing coach for the two-time major winner, saying the breakup was mainly down to the coronavirus pandemic.
The New York-based Parada had been working with Ko over video calls during the break to the season.
"It is what it is," he said. "I was really excited about the restart. I felt like things were going in a really good direction. She was swinging it in a way that looked really fantastic.
"I felt like she was swinging it closer to when she was 16-17 than she had in a really long time.
Parada said Ko told him that she appreciated their time working together and that she wanted to get other advice ahead of the restart of the golfing season.
"She just gave me a call and I thought she was gonna call me to FaceTime me and do some swing work for an hour or half hour or so. [But] she called me and told me [the news].
"I don't know exactly what the reasoning was. I know we ended up on very good terms."
Ko is set to tee off in the LPGA Drive On Championship event starting Friday.
NZME understands her new coach is now Sean Foley who has previously worked with Tiger Woods and Justin Rose.
Parada was the latest coach enlisted by the Kiwi to try and turn around a rough stretch of form that has seen her fall to 52nd in the world rankings – a far cry from her peak when she held the number one spot for 84 weeks.
Ko has worked with Gary Gilchrist, Ted Oh, Dave Whelan and Parada since sacking David Leadbetter in 2016.
Leadbetter, who has long been critical of the role that Ko's parents, Gil Hong and Tiny Hon, have played in their daughter's career, urged Ko last year to "leave the nest" and take control of her own career – even calling the situation "unbelievably ignorant".
