She was born Beryl Clutterbuck in England. At the age of three her parents moved to Kenya, then British East Africa, where she spent an adventurous childhood playing and hunting with native Africans, and, on her family's farm, developing a knowledge of and affection for horses.
As a young adult, she trained horses and became a bush pilot. These experiences were chronicled in her critically acclaimed memoir, West With The Night, published in 1942 (although some have questioned whether Markham was, in fact, the author of this work).
After living for many years in the United States, Markham moved back to Kenya in 1952, and died there in 1986.