[1] He then played one season in 1945–46 for the University of Southern California (USC) under head coach Sam Barry.

[7] At Lindsay, Kloppenburg emphasized defense and ball control in a coaching style inspired by Hank Iba and Pete Newell.

[16][17] In the 1976–77 season, Kloppenburg left U.S. International to coach for Dutch team Nationale Nederlanden Donar.

[8][16] Beginning in 1978, Kloppenburg coached the Marine Corps Base Camp Pendleton basketball team and scouted for the Houston Rockets.

[8][21] The SuperSonics made the playoffs in all but two years (1986 and 1990) and qualified for the Western Conference Finals in 1987 and 1993 during Kloppenburg's second stint.

[21] Beginning January 15, 1992, Kloppenburg served as interim head coach of the SuperSonics after the firing of Jones.

[26] Kloppenburg is regarded as the innovator of the SOS defensive system, known for its ability to create turnovers because of "contact switching" on every screen and intense ball pressure with trapping principles.

[13] They have two children, including Gary Kloppenburg, a head coach for the WNBA teams Tulsa Shock (2012–2013) and Seattle Storm (2017, 2020–present).

Granddaughter Carlotta Kloppenburg-Pruitt has been an assistant women's basketball coach at San Jose State since 2018.