Sjef Janssen was a professional racing car driver 1946 until 1954. 1947 and 1949 he became Dutch champion in the road race in the pros, after he had already won the 1944 national title of " Independent ". The Road World Championships 1947 in Reims, he won the bronze medal.
Twice, in 1947 and 1949, Janssen launched at the Tour de France. In 1947, the first staging of the tour after the Second World War, he was the only one of six Dutch participants, who arrived in Paris. He was ranked 32
After ending his active cycling career Janssen worked as sports director and led a bike shop in his hometown Elsloo. To date, he has worked as a consultant, such as a test team of selected riders of the Tour Wieler clubs Grensland, the " Triple T Team ".
Sjef Janssen is the father of Sjef Janssen Jr., the coach of the Dutch dressage rider and husband of the multiple Olympic champion Anky van Grunsven.