Konrad Knudsen was the son of a painter. He studied the subject Auditing ( Handelsskole ) and worked as a painter in Drammen, before he traveled to the U.S. in 1908. There he earned his living as a painter, lumberjacks and construction workers. He eventually became editor of a national newspaper, which appeared in the Norwegian language.
1920 Knudsen returned back to Drammen. Until 1923 he worked as a painter, he got a job as editor of the newspaper Fremtiden. From 1921, he held various positions within the Labour Party. In 1937 he was elected to the Norwegian Parliament, where he served until 1957.
In 1935 he invited Leo Trotsky to Norway. Trotsky lived initially in Knudsen's house in Norderhov, outside the small town of Hønefoss. After a slump Norwegian fascists, the government intervened and Trotsky moved to command the Minister of Justice and later UN Secretary-General Trygve Lie.
During the Second World War, Knudsen held first in Sweden, then Canada, and finally in the United States. He worked for an information service from the Norwegian Government and the Supreme Court of Norway.
From 1949 to 1957 he was chief auditor of Norway.