 Nielsen was also a member of Aker municipal council.He chaired the employers' association "De norske Tekstilfabrikanters Forening" from 1899 to 1901 and "Den norske Fællesforening for Haandverk og Industri" from 1901 to 1912, and was a central board member of the Norwegian Employers' Confederation from 1900.He was also a board member of Akers Sparebank, and bank director from 1906 to 1910.