Following the news of his death, NBA commissioner David Stern said in a statement, "We are saddened by the passing of Darell Garretson. Darell was a man of extraordinary character, who touched many lives during his 31-year tenure as an NBA official and supervisor of officials." Lamell McMorris, spokesman for the National Basketball Referees Association (NBRA), the union representing NBA officials, said, "Our grief at losing Darell Garretson is not just about the loss of an icon, a refereeing legend, although he certainly is both of those things. It is much more personal. Darell discovered and developed so many of our current referees. ... He took them and he coached them, tirelessly, and he made them some of the most elite referees in the world. And they love him for it."
Later when he became officiating supervisor, Garretson was an advocate for increasing the number of officials per NBA game from two to three, beginning with the 1988-89 NBA season. The addition of the third official allowed for better coverage of the court and also provided mentoring for younger officials with two more experienced officials.
Working in the NBA's front office, he also was involved with scouting prospective officials and providing instruction. He developed the concept of “refereeing the defense,” a practice in which officials focus attention on a defensive player instead of watching the ball. He urged all officials to continue improving skills and achieving personal goals by focusing on every possible aspect. Former referee and current director of officiating, Ronnie Nunn said of Garretson, "[he] was a guy who drilled into you to get plays right."
As an official and supervisor in the NBA, Garretson was the target of criticism by the media and notable officials including, Jake O'Donnell, Richie Powers, and Earl Strom. Critics of Garretson claimed that he developed the current generation of referees into "robots" by suppressing individual personality. On the court, Garretson was also known to minimize the amount of communication between himself and players and coaches, which was considered an unpopular approach among members of the media.