Nicoll was born at the Manse in Kelso, Scotland, the son of William Robertson Nicoll, a minister of the Free Church of Scotland. He studied science at Cambridge before going on to St. Bartholomew's Hospital and then to Vienna, Berlin and Zurich where he became a colleague of Carl Gustav Jung. Jung's psychological revelations and his own work with Jung during this period left a lasting influence on Nicoll as a young man.

After his Army Medical Service in the 1914 War, in Gallipoli and Mesopotamia, he returned to England to become a psychiatrist. In 1921 he met Petr Demianovich Ouspensky, a student of G. I. Gurdjieff and he also became a pupil of Gurdjieff in the following year. In 1923 when Gurdjieff closed down his institute, Nicoll joined P.D. Ouspensky's group. In 1931 he followed Ouspensky's advice and started his own study groups in England. This was done through a program of work devoted to passing on the ideas that Nicoll had gathered and passing them on through his talks given weekly to his own study groups.

Many of these talks were recorded verbatim and documented in a six-volume series of texts compiled in his books Psychological Commentaries on the Teaching of Gurdjieff and Ouspensky.

Nicoll also authored books and stories about his experiences in the Middle East using the pseudonym Martin Swayne.

Though Nicoll advocated the theories of the Fourth Way he also maintained interests in essential Christian teachings, in Neoplatonism and in dream interpretation until the end of his life.

Books by Nicoll

• Psychological Commentaries on the Teaching of Gurdjieff and Ouspensky, Boston: Shambhala, 1996, and Samuel Weiser Inc., 1996, ISBN 0-87728-910-7 (6 volumes)
• Dream Psychology
• Living Time and the Integration of the Life
• The Mark
• The New Man : An Interpretation of Some Parables and Miracles of Christ
• Informal Work Talks and Teachings
• In Mesopotamia (under the pen-name of 'Martin Swayne')

Short stories by Nicoll under the pen-name Martin Swayne

• "A Game of Consequences", London Magazine, October 1911
• "The Black and Gold Curtain", London Magazine, April 1912
• "The Mystery of the 'Vathek'", Pall Mall Magazine, January 1913
• "Life-Like", The Strand Magazine, February 1913
• "The Piano-tuner", London Magazine, April 1913
• "Sir Clifford's Gorilla", The Strand Magazine, July 1913
• "The Alabaster Jar", The Strand Magazine, August 1913
• "The Flying Log", London Magazine, November 1913
• "The Corot Landscape", The Strand Magazine, November 1913
• "Half a Ton of Dynamite", The Strand Magazine, January 1916
• "The Sleep-Beam", The Strand Magazine, March 1918
• "The Whistling", Lloyd's Magazine, October 1918
• "An Awkward Situation", The Strand Magazine, July 1924
• "A Sense of the Future", The Strand Magazine, August 1924
• "An Obvious Case", The Strand Magazine, October 1924