The Australian Open champion, who split with former coach Sascha Bajin earlier this month, made the announcement on social media but did not elaborate on Jenkins' exact role.
"Had a great dinner with the team. Also taking this moment to thank Jermaine for joining us and coming on board," she wrote, alongside a photograph of herself with Jenkins and other members of her team.
Jenkins, who was recently appointed as the United States Tennis Association women’s national coach, was formerly the hitting partner of Venus Williams.
Osaka split with Bajin after winning the Australian Open last month.
The 21-year-old enjoyed a spectacular rise during the time they worked together, becoming the first Japanese player to win a grand slam when she beat Serena Williams in the U.S. Open final in September.
(Reporting by Jack Tarrant; Editing by Amlan Chakraborty)
