Following a successful 1977 season as an amateur, including the national amateur title, Daniel Willems joined professional team IJsboerke. In his first years, he immediately proved himself as a great sprinter, particularly in the one classics, but later proved fit for multi-stage events. In 1982, Willems finished 7th in the Tour de France final classification, having also won two stages, just like in the Tour of 1981. In the 1979 World Championships, Willems came close to winning the Rainbow Jersey, as he led the charge to the finish with less than 2 km to go but crashed into Knut Knudsen and had to retire. Willems did win two major classic races, Paris-Tours (1980) and Flèche Wallonne (1981), as well as a host of minor races. His pro career was brief, though, and he retired in 1985 after several uneventful seasons.