McCaw officially joined the Cavaliers' roster on Monday, Dec. 31 after Golden State decided not to match Cleveland's offer.
The circumstances were freaky and raised questions about Cleveland's motivation to sign and release a player off the roster of their frequent NBA Finals rival.
The Cavaliers signed McCaw to an two-year, non-guaranteed $6 million contract that the Warriors declined to match. The New York Times first reported the Warriors' complaint and investigation.
A person with knowledge of the situation told The Associated Press on Tuesday that the league has opened a review at the request of the Golden State Warriors, the team with which McCaw spent the previous two seasons. It's unclear how long the NBA's review will take, or what - if anything - the Warriors are seeking. The Cavaliers signed him on December 30 to a two-year, $6 million non-guaranteed deal, with the Warriors choosing not to match those terms.
On Sunday, the Cavs waived McCaw after three games in Cleveland ahead of a deadline that would have guaranteed his contract.
The Warriors, who weren't interested in McCaw and allowed him to stretch his free agency into the start of the season, now want the league to look into Cleveland's actions.
The day the Cavaliers signed Patrick McCaw, they had nine healthy players available for a game that night in Miami.
Some have speculated the Cavaliers made the moves to spite the franchise that beat them in three of the past four NBA Finals.