A printer by profession Louis Pfenninger was also an amateur cyclist who competed during the late 1960s and the early 1970s. Pfenninger had some good results in races in his native Switzerland, along with a third-place finish on the seventh stage of the 1964 edition of the Milk Race in England. These earned him a place on the Olympic team for the Tokyo Games, where he placed 39th in the road race, only 0.13 seconds behind the race winner. Pfenninger had his best results at home, winning the Tour de Suisse in 1968 and 1972, and becoming the Swiss road champion in 1971. By the mid-1970s he had retired from cycling and he later moved to Spain.