Between 1971 and 1983 Monsels won seven Dutch sprint championships in the 60 metres (indoor) and the 100 and 200 metres (outdoor). Representing the Netherlands, Monsels reached the final of the 60 metres at the 1973 European Athletics Indoor Championships in Rotterdam, finishing fifth. In 1972 and 1976 he competed in the Olympic Games, representing Suriname, reaching the second round of the 100 metres and 200 metres on both occasions. In the late 1970s Monsels quit competitive athletics for a while, but returned in the early 1980s. In 1982 he represented Suriname at the Central American and Caribbean Games in Havana.