Detlef Kästner was an East German light-middleweight boxer who earned a bronze medal at the 1980 Moskva Olympics. There, he lost his semi-final against Soviet Russian Aleksandr Koshkin by a 5-0 decision. The same year, he earned his only East German national title. One year later, he again lost to Koshkin at the Europeans in the eighth-final.
In 1984, Kästner retired from boxing. He later became facility manager at Sportforum Höhenschönhausen, where handball club Füchse Berlin held their training sessions and other sportspersons from Berlin regularly used the training facilities.