Feddersen started his career as a volunteer at the Supreme Court. In 1830, he became a trainee lawyer () at the Attorney General. In 1831, he won the University of Copenhagen's gold medal. In 1832–35, he received a public grant to go on a study trip abroad. In 1835, he became employed as a military prosecutor () at the King's . In 1836, he published . The latter publication was instrumental in having him appointed as one of the directors of Copenhagen's Poor Authority () in 1837. In 1844–45, he was vice chairman of (Copenhagen Industrial Society) in Copenhagen. 1841 saw him elected as one of Copenhagen's members of Østifternes Stænderforsamling, whose secretary he became. Feddersen was appointed as
Governor of the Danish West Indies in 1851. He left the post in 1855 and returned to Denmark. He was succeeded by
Johan Frederik Schlegel. Back in Copenhagen, he joined the management of
Sparekassen for Kjøbenhavn og Omegn (1856–62). He was also elected as a
Member of Folketinget in Copenhagen's 3rd Constituency. ==Personal life==