The deal between the 76ers and Horford was worth $109 million, which includes $97 million in guaranteed money and $12 million in bonuses, ESPN reported.
Deals cannot become official until July 6 because of the league's annual moratorium.
Horford's risk -- opting out of a $30 million contract with the Boston Celtics -- is apparently paying off. The forward played the last three seasons with the Celtics and earning an All-Star appearance during that time.
Last season, he averaged 13.6 points, 6.7 rebounds and 4.2 assists per game in Boston. He helped the Celtics get to the first round of the playoffs, but the team was eliminated by the Milwaukee Bucks in the Eastern Conference semifinals.
The 76ers were among the teams who were reportedly interested in him once Horford decided to leave Boston.