Mitchell died in San Antonio after the former Auburn star fought the disease for two years, said his son, Mike Mitchell Jr.
Mitchell averaged 19.8 points and 5.6 rebounds during his career. He was an All-Star in Cleveland in 1981 but had his winningest years in San Antonio, playing alongside George Gervin and Artis Gilmore.
"We have a great deal of respect and admiration for Mike Mitchell," said Spurs coach Gregg Popovich. "He was a good man who cared deeply about his family and the community of San Antonio."
The Spurs reached the Western Conference Finals in 1982 and 1983 but fell to Magic Johnson and the Los Angeles Lakers both times. It was the farthest San Antonio would advance in the playoffs until David Robinson put the Spurs back in the conference finals a decade later.
A first-round draft pick in 1978, Mitchell spent 3½ seasons in Cleveland before being traded to the Spurs. He averaged 24.5 points during his one All-Star season, which took place while the Cavaliers were among the league's worst teams.
Mitchell played more than a decade in Europe after his NBA career ended in 1988.