He was born in London.
He became Aleister Crowley's secretary in 1928. In 1932 Crowley and Regardie part company.
When the Hermetic Order of the Golden Dawn scattered, he took all the order documents he could get and compiled The Magical System of the Golden Dawn (The Golden Dawn for short), which earned him the accusation of being an oath-breaker, and the branch of Golden Dawn magic its continuing existence and popularity. Other works include A garden of pomegranates, The Middle Pillar and The Tree of Life.
He died in Sedona, Arizona.