He was born on February 26, 1859, in Charlottetown, Prince Edward Island. He graduated from the University of King's College in Nova Scotia, and served as an Episcopal rector at St. Luke's Pro-Cathedral in Halifax, Nova Scotia, and later at Christ Church in Cambridge, Massachusetts.
King retired from the clergy in 1900 due to illness, and began writing. His anonymously published novel The Inner Shrine, about a French Irish girl whose husband is killed in a duel, became very popular when published in 1909. King wrote a number of best-selling works (see list below). Critics often faulted Kings fiction for its sentimentality and didacticism.
King's spiritual orientation increased later in his life. His The Abolishing of Death (1919) described the transmission of messages from a deceased chemist. The Conquest of Fear (1921) portrayed his own struggle with ill health and eventual spiritual growth, and lays out his somewhat mystical approach to religious understanding.