"Hey everyone, I will no longer be working together with Sascha", Osaka said.
Osaka won her first WTA title at the BNP Paribas Open, last March, following which she went on to clinch 2018 US Open title and 2019 Australian Open. Under Bajin's tutelage, she held her first title in at Indian Wells in March previous year and made her major breakthrough at Flushing Meadows by defeating Serena Williams in the final.
Bajin, a former hitting partner to Serena Williams, responded: "Thank you Naomi".
Osaka hired Bajin ahead of the 2018 WTA season and the pair didn't take long to click on court.
Osaka, who is scheduled to compete in Dubai next week, began sounding out potential replacements late a year ago, local media reported.
The US-based player has enjoyed a meteoric rise to the big time after rising from 72 in the world to number 1 in the past 12 months.
Under Bajin, Osaka won both the US Open and the Australian Open to rank World No. 1.
She was born in Japan - her mother is Japanese, her father is Haitian - before moving to the United States when she was three years old.