The sign-and-trade agreement creates a $28.5 million trade exception for the Celtics, the largest in NBA history. The Celtics will get Charlotte's draft pick only if the Hornets finish in the top five in the league next season, so it's unlikely they will get anything in the deal other than unloading Hayward's contract.
Hayward, 30, declined his $34.2 million player option with Boston earlier this month, ending a tumultuous three-year run with the team, then agreed to a four-year, $120 million deal with the Hornets.
"We are thrilled to welcome Gordon and his family to the Hornets organization and Charlotte," general manager Mitch Kupchak said in a statement. "Gordon is an NBA All-Star, a proven scorer and playmaker and a tough competitor that will fit well into the needs of our team. We believe that his basketball talent, NBA experience and veteran leadership will make a positive impact on our young, talented team as it continues to develop."
To help make room for Hayward's salary, Charlotte waived Nicolas Batum. The final year of his deal will be stretched over the next three seasons as a yearly $9 million dead cap hit. The Hornets also waived forward Ray Spalding.
Hayward, a 10-year NBA veteran, has appeared in 641 regular-season games with 479 starts with the Jazz and Celtics, averaging 15.3 points, 4.4 rebounds and 3.5 assists in 30.8 minutes per game. The 6-foot-7 forward has appeared in 29 postseason games with 16 starts, averaging 15 points, 4.6 rebounds and 2.9 assists in 33 minutes per game.
ESPN's Bobby Marks and The Associated Press contributed to this report.