Majerus turned professional in 1936: that year he also made his Tour de France debut, however he was eliminated at the end of the 13th stage.
[2][1] He was, however fit for competition by the time of that year's road world championships, where he was part of the winning breakaway but missed out on the podium in the final sprint, finishing fourth.
At the entrance to the velodrome where the stage finished, Jean-Marie Goasmat attacked from the lead group, but was hauled back by Majerus who pipped him to the line.
He briefly continued competing after the war, winning the 1946 Grand Prix de Lorraine and the 1947 Luxembourg national individual pursuit title on the track.
[1] After retiring from competition, between 1949 and 1952 he served as driver for Nicolas Frantz in the latter's role as technical director for the Luxembourg national team in the Tour de France.