Birgit Treiber was mainly a backstroke swimmer but also swam individual medley. At the 1976 Montréal Olympics she won silver medals in both backstroke events behind her teammate Ulrike Richter. She also finished an unfortunate fourth in the 400 metres individual medley and swam the heats with the East German 4x100 medley relay. Four years later at Moskva Treiber added a bronze medal in the 200 backstroke. She set four world records during her career, three in the 200 back and one in the 400 IM.
At the World Championships Treiber won one gold and four silver medals, while at the European Championships she won another three gold medals in 1977. She also won East German national titles in the 100 back in 1977 and 1978, and in the 200 back from 1975-80. After German re-unification, former East German officials admitted to administering doping to nearly all their swimmers, including Treiber. By profession, she later became a dentist with her own practice in Leipzig.