He was born in Tromøy as a son of shipmaster and accident investigator Peter Olsen (1866–1950) and Louise Holm (1885–1969).
[1] He finished his secondary education at Frogner School in 1932, studied at the University of Oslo and graduated in 1940 with the cand.philol.
His master's thesis Den gammelnorske oversettelse av Pamphilus was published in the same year.
Holm-Olsen specialized in Old Norse philology and was a research fellow from 1945 and docent from 1949, both at the University of Oslo.
He also contributed to Norges litteraturhistorie and released more popular books such as Lys over norrøn kultur (1981) and Med fjærpenn og pergament (1990).