Rasmussen was born in Jakobshavn, Greenland, the son of a Danish missionary, the vicar Christian Rasmussen, and an Inuit–Danish mother, Lovise Rasmussen (née Fleischer).
He had two siblings.

Rasmussen spent his early years in Greenland among the Kalaallit where he learned to speak Kalaallisut, hunt, drive dog sleds and live in harsh Arctic conditions. "
My playmates were native Greenlanders; from the earliest boyhood I played and worked with the hunters, so even the hardships of the most strenuous sledge-trips became pleasant routine for me."

He was later educated in Lynge, North Zealand, Denmark.
Between 1898 and 1900 he pursued an unsuccessful career as an actor and opera singer.
Rasmussen was born in Jakobshavn, Greenland, the son of a Danish missionary, the vicar Christian Rasmussen, and an Inuit–Danish mother, Lovise Rasmussen (née Fleischer). He had two siblings.
Rasmussen spent his early years in Greenland among the Kalaallit where he learned to speak Kalaallisut, hunt, drive dog sleds and live in harsh Arctic conditions. "My playmates were native Greenlanders; from the earliest boyhood I played and worked with the hunters, so even the hardships of the most strenuous sledge-trips became pleasant routine for me."
He was later educated in Lynge, North Zealand, Denmark. Between 1898 and 1900 he pursued an unsuccessful career as an actor and opera singer.
Knud Rasmussen