The royal's chain Balance, which he started in 2006, has had low profitability for several years and made a loss last year.
According to Dagens Industri, the new buyer is Sats, one of the largest gym chains in Sweden, which will take over the three gyms and hopes to turn Balance's fortunes around.
The prince had remained the main owner of Balance but hasn't been active on its board since 2010, when he married Crown Princess Victoria. The exact amount Prince Daniel and the other three owners will get from Sats has not been made public.
Daniel met Victoria when the royal started working out at another of the gyms he owned in 2002, and the pair married eight years later. Daniel remains a part-owner of that chain, though he was no longer allowed to work at the gyms following his marriage.
The couple have two children, Estelle, whose first day at school was on Tuesday, and younger brother Oscar.
In public life, Daniel works to encourage young people to consider becoming entrepreneurs, visiting high schools around the country alongside prominent Swedish business owners with the Prince Daniel Fellowship and Entrepreneurship Program.
READ ALSO: Who's who in the Swedish royal family