Gerschwiler made his international debut at the 1939 European Championships, where he placed 5th. Between 1939 and 1947, no international skating competitions were held, due to World War II. Gerschwiler had been living in England with his uncle and coach Jacques Gerschwiler when the war broke out. When his uncle was called home to Switzerland, Gerschwiler stayed with Cecilia Colledge's family. He spent the war years working as a factory worker and fire watcher and was able to practice skating only once a week.
Following the War, Gerschwiler emerged as one of the dominant skaters of the time.
Until Stéphane Lambiel won his first world title in 2005, Gerschwiler was the only Swiss man ever to have been World Champion. He and Lambiel are the only Swiss figure skaters ever to have won a silver medal at the Olympics. The only other Swiss skater to medal at the Olympics was Georges Gautschi who won bronze in 1924. Following Lambiel's win in 2005, Gerschwiler sent him a congratulatory message.