Rien Poortvliets talent for drawing was evident at a young age. His strictly Calvinist parents, however, were not amused by the idea of their eldest son becoming an artist. After high school and military service, Poortvliet immediately started working at Unilever's advertising agency. But Poortvliet, a passionate hunter and nature lover, found greater joy in his work as an illustrator for various publishers. In the late 1960s, he was able to afford to start working as an independent illustrator for books and magazines such as 'De Nederlandse Jager' (The Dutch Hunter) and the German magazine 'Wild und Hund'. (Wild animals and Dogs) His animal illustrations are preceded by thorough preliminary studies and lengthy observations. His work is so striking that publisher 'Unieboek' asked him to illustrate books for them full-time in the late 1960s. In 1972, Poortvliet decided to compile a book of his own hunting experiences. He provided text for his drawings and watercolors of birds and other woodland creatures, rather than illustrating someone else's. Thus, he became a 'drawing storyteller'. Poortvliet achieved great national and international success with his books and animal calendars, and he was a welcome guest on Dutch television. In books like 'Along the Garden Path of My Fathers' and 'He Was One of Us', he took us back in time, traveling extensively throughout the country to record memories. His faith was a common thread throughout his life, and he passionately expressed it in his books. Poortvliet wrote and illustrated some 25 books, including his well-known 'Kabouterboeken' (Gnome Books) which have been published in numerous languages. He was also friends with the Royal Family and regularly went hunting with Prince Bernhard.
In 1992, the Rien Poortvliet Museum opened in Middelharnis. 'Fortunately, far away from the modern art scene in Amsterdam', as Poortvliet said in an interview. After this museum closed in 2006, a new location was found on the island of Tiengemeten.