Nielsen received his education in a private school, followed by a year in 1869–1870 at Vejstrup College and then Gedved Seminarium.

In 1884, he became member of the Committee for Svendborg Nyborg railways, and later promoted to director and in 1903 to Executive Chairman.

The same year, he succeeded his father as director of the Agricultural Bank of Fyn.

In 1884, Nielsen also became part of financial division of Svendborg County, but had to abandon this post three years later due to political tensions.

In 1900 he was hired as director of fire insurance in Svendborg and held this post until his death in 1928.