Janwillem van de Wetering was born on February 12, 1931, in Rotterdam, Netherlands, the son of Jan Cornelius van de Wetering, a businessman, and Catherine van de Wetering. He studied at the Delft Institute of Technology, the College for Service Abroad, Cambridge University, and the University of London. In 1954, he was married to Edyth Stewart-Wynne, from whom he was later divorced. He was married to Juanita Levy in December of 1960; a daughter, Thera, was born to them.
Van de Wetering spent more than fifteen years of his life as a businessman, beginning as a salesperson for Dutch companies in South Africa in 1952. Then, in 1958, he became a layperson in a Zen monastery in Kyoto, Japan, for a year. This put an end to what he has described as the “beatnik sort of life” that he had earlier led. In 1959, he returned to his business career, serving as the manager of a company in Bogotá, Colombia, until 1962; later he worked in Lima, Peru. He also worked as a real estate salesperson in Brisbane, Australia. After returning to the Netherlands in 1965, he became manager of the family textile business, which had been failing, and restored it to profitability. As an alternative to military service, he joined the Amsterdam Reserve Police, where he rose from the rank of patrol officer to sergeant. Van de Wetering has made very good use of his Amsterdam police experience. Almost all of his novels are set in Amsterdam, and as he has admitted, “All my novels are built on police reports.”
In 1975, van de Wetering left Amsterdam for Maine. He joined a Buddhist group in New England, remaining a member until 1980. He has contributed to several magazines in the United States and the Netherlands and has also written plays for Dutch television. Both Tumbleweed (1976) and Outsider in Amsterdam (1975) have been produced as films.