Kotz, a 6'3 forward from Rhinelander, Wisconsin, played collegiately at the University of Wisconsin–Madison from 1940 to 1943. As a sophomore, Kotz led the Badgers to the 1941 NCAA Championship and was named tournament Most Outstanding Player. He was an All-American in 1942 and 1943. Kotz left Wisconsin as the school's leading scorer.
He was inducted into the University of Wisconsin Athletics Hall of Fame in 1991.