"Our thoughts are with Brad's family on this extremely sad day for them, the ATP and the entire international tennis community. He will be sorely missed by all," the ATP, which oversees the men's professional tennis tour, said in a statement.
Drewett, who died at his home, had led the ATP since January 2012. He said in January he would remain in both positions until the ATP Board of Directors found a successor.
He had been part of the ATP for 35 years, beginning as a player. His posts included the tournament director of the ATP World Tour Finals.
Drewett was ranked in the Top 40, winning a pair of tournaments, and reached No. 18 in the doubles rankings in 1988. He was on seven doubles tournament title teams.