Hailing from West-Berlin, Rudi Hornig fought for Post SV (presently Pro Sport Berlin 24). Competing as a middleweight for most of his career, Hornig claimed West German amateur boxing titles in 1965, 1967 and 1969. In 1972, he competed in the light-heavyweight, winning his fourth and final national title and earning a ticket for the Olympics in München. There, Hornig was eliminated in the quarter-finals, equalling his best international performance. He had achieved the same feat at the 1967 Europeans.
West Germany