Born in Kristiania (now Oslo), he established Norway's first correspondence school and his own publishing house.
His father was gardener Carl Gustav Mortensen (1850–1899) and his mother Anna Kristine Solberg (1855–1930).
He married Anne Marie Damnæs (1886–1960) at an unknown point, with whom he had the son Finn Mortensen (1922–1983).
It published many foreign-language book series that had not been translated into Norwegian before, amongst them Tolstoy's collected works in twelve volumes.
Magnus Andresen, who acquired Norsk Ukeblad, experienced economic loss with the acquisition, and sold it back half a year later.