Leo Karner had a long amateur career at the top levels of Austrian cycling, lasting from 1971-82. In 1973 he placed second in the Austrian amateur road race championship, which he would repeat in 1978. He rode in the Tour of Austria nine times between 1971-82, placing fourth in 1977 and 1979, and fifth in 1976. Karner raced the Tour de l’Avenir in 1973 and 1979, but did not finish either time. He also rode the 1974 Peace Race, placing 72nd, and raced four times in the Uniqa Classic (1978-79, 1981-82), placing second in 1979.