Educated at the School of Gustav Bachmann from 1935-1938. Later educated at the Royal academy of arts in 1940. Nielsen was strongly influenced by the early European fauvists and modernists. Nielsen worked with landscapes and portraits but was most known for his still-lifes. Nielsens works are often defined by simple and clear light colors. Nielsen worked primarily in Scandinavia but has also worked and traveled in Spain and Greece from 1950, where he worked on Cubist landscapes. Other travels include Paris, southern France and Italy. Nielsen worked with graphic designs as well as paintings and won the art awards: The Queen Alexandra and the Claudi-Pedersen in 1972 and 1977.
The Artists Fall Exhibition: 1951.
The Atheneum: 1953-1959.
The Aarhus Winter Exhibition: 1961-1969.
Gallery Gl. Strand: 1970-1983.
The townhall: 1950-1973.
The Carlsberg Museum: 1979.