He grew up with a background in both the Inner Mission and the Methodist Church, and was Candidatus theologiæ at the University of Oslo 1953.
He was a Methodist priest in Harstad 1956–1958, research fellow from 1958 to 1962 and professor at Wesley Theological Seminary in Washington from 1962.
In 1973 he was appointed professor at the University of Trondheim specializing in the New Testament and religion of the Greco-Roman world.
Borgen was a Knight of the Order of St. Olav in 1998[2] and Member of the academy and of the Royal Vetenskapssamhället, Uppsala.
"In 2003 he was awarded the Gunnerus Medal, which is the highest honour given by The Royal Norwegian Society of Sciences and Letters.