Weeks after winning the NBA championship, Boston Celtics' majority owner announces plans to sell the team.

• The Boston Celtics have been put up for sale by Boston Basketball Partners LLC, as announced on social media site X on Monday.
• The ownership group's majority stake is expected to be sold by the controlling family, with completion anticipated either later this year or in early 2025.
• In 2002, Wyc Grousbeck led the ownership group to acquire the Celtics. He anticipates remaining the governor of the team until the second closing of the deal in 2028.

The National Basketball Association champions are up for sale.

The Celtics' ownership group has announced plans to sell the team, as stated on their X social media account.

Boston Basketball Partners LLC's controlling family plans to sell all of its shares in the team for "estate and family planning purposes."

It is anticipated that the sale of a significant portion of the company will be completed by the end of 2024 or early 2025, with the remaining portion of the sale taking place in 2028, as stated.

The Celtics, one of the most successful and widely followed U.S. professional sports teams, could command a high price as sports franchise valuations rise, having won their 18th NBA championship last month.

In 2002, Wyc Grousbeck led a group of buyers to purchase the Celtics for $360 million. As a native of Massachusetts and devoted Celtics fan, Grousbeck intends to continue serving as the team's governor until the second closing in 2028.

Grousbeck is also a member of the ownership group for the tequila brand Cincoro, which is also owned by other NBA team owners and Hall of Famer Michael Jordan.

Grousbeck and his team did not immediately respond to requests for comment from their representatives.

Sports valuations, media rights climb

In June, the Celtics emerged as NBA champions after defeating the Dallas Mavericks in Game 5 of the Finals. This marked their second championship under Grousbeck's ownership.

When owners sell a stake or the entirety of their U.S. professional sports teams, especially those in the NFL and NBA, they often receive high valuations.

In 2023, the NBA's Phoenix Suns and WNBA's Phoenix Mercury were sold to Matt Ishbia for a record valuation of $4 billion.

The biggest TV audiences are drawn to live sports, making the media rights for the leagues increasingly valuable.

The ongoing negotiations for the NBA's media rights are expected to result in an announcement soon, with NBCUniversal reportedly set to pay $2.5 billion per year, alongside ESPN and Prime Video among other bidders.

— CNBC's Jessica Golden contributed to this article.

Disclosure: NBCUniversal is the parent company of CNBC.