Winfrey, 67, discussed her joint venture with the Duke of Sussex while appearing on "The Drew Barrymore Show" alongside psychiatrist Dr. Bruce D. Perry.
"I want to just say that Dr. Perry and I have been also, for the past two years, along with Prince Harry and Apple, we've been working on this mental health series that's coming out in May on Apple," Winfrey said (via Daily Mail).
According to the outlet, the series will be a show about "mental illness and mental wellness." It was first announced back in April 2019 and Harry has been named as a "co-creator and executive producer" of the series.
Reports say the series was initially to be released in 2020 but was hit with delays due to the ongoing pandemic. It doesn't appear a set date has yet to be shared by the streamer. A rep for Apple TV+ did not immediately return Fox News' request for comment.
Winfrey discussed the series and how it came to fruition back in 2019 in a chat with her friend Gayle King.
"I asked [Prince Harry] the question, 'What do you think are the most important issues facing the world right now?' and he said, 'There are two,'" Winfrey recalled via the outlet. "He said climate change and mental wellness, mental fitness and mental health."
Meanwhile, Harry spoke to the significance of the series in 2019 with podcast host and journalist Bryony Gordon.
"If the viewers can relate to the pain and perhaps the experience, then it could save lives, as we will focus on prevention and positive outcomes," Harry said at the time.
Harry added that he and Winfrey have held discussions with experts and plan to present "the facts and science" that exist around mental health.
This is certainly not the first time Winfrey and Harry have combined forces. Back in March, nearly 50 million people around the world tuned into Winfrey's two-hour sit-down interview with Harry and his wife, Meghan Markle.
In the interview, Markle, 39, said a member of the royal family discussed the color of her and Harry's then-unborn son's skin. Prince Harry later revealed it was not Queen Elizabeth nor his grandfather, Prince Philip, who made the remark. The Duke of Sussex also said he'd never reveal the family member's identity.
Harry also told Winfrey there's currently "space" between him and his brother Prince William. He also claimed his father, Prince Charles, had stopped taking his calls.
Winfrey later called it a "powerful" interview due to the couple's ability to be "open," "vulnerable" and "truthful."
The Sussexes announced their decision to step back as senior members of the royal family in early 2020.