After graduating from Shawnee High School, Don Sumner became one of Bob Bass' early recruits and helped lead the Bison to the co-championship of the Oklahoma Collegiate Athletic Conference in 1957, the school's first league title, and to OBU's first NAIA District 9 championship and first trip to the NAIA National Tournament in 1958.

A 5-11 guard noted for driving to the basket, Sumner established a remarkable OBU free-throw record in the 1956-57 season, hitting 236 of 262 attempts—90.1 percent. For his four-year career he hit 555 of 668 charities—83.1 percent.

He scored 1,343 points and averaged 12.9 points in his career. In 1957, he scored 478 points, a season record at that time, and averaged 16.4 points.

Sumner was a first team all-conference selection in 1957 and a second team pick in 1958.

He also was a member of the OBU golf team for three seasons.

Sumner coached and taught science at Shawnee High School from 1958-61 and then became head basketball coach at St. Gregory's University from 1961-1995, compiling a record of 621 wins and 464 losses. In 1971, he was named the National Junior College Athletic Association's Region II Coach of the Year.

While coaching at SGU, he taught biology, zoology, and nutrition. He was SGU athletic director from 1970-1996 and from 2006-2012. He became athletic director emeritus in 2012 and lives in Shawnee.