He participated almost annually in the Autumn Exhibit between 1883 and 1911, and held notable exhibitions in Christiania Kunstforening (1895, 1906, 1924, 1931), at the 1862 International Exhibition, the Exposition Universelle of 1889 and in Munich in 1913. Eleven of his works are owned by the National Museum of Art, Architecture and Design. He is also represented in Mandal Kunstforening and Mandal Bymuseum, but is perhaps best known for the collection of about 300 works which was donated to Oslo municipality by Nielsen's heirs in 1933. Since 1994 this collection is on permanent exhibit in the Stenersen Museum. Nielsen was also decorated as a Knight, First Class of the Royal Norwegian Order of St. Olav in 1890. The square "Amaldus Nielsens plass", which includes a bust of Nielsen, was named after him.