Background
Berthelsen was born in Sør-Audnedal.
politician member of the Parliament of Norway
Berthelsen was born in Sør-Audnedal.
He was elected to the Norwegian Parliament from the Market towns of Telemark and Aust-Agder counties in 1945, and was re-elected on one occasion. He then sat as a regular city council member in the periods 1940–1944 and 1945–1946.
Berthelsen was a deputy member of the executive committee of Arendal city council from 1934 to 1940. He was later a member of Bergen city council during the term 1955–1959.