Sinnett's father died while he was young, by 1851 Sinnett is listed as a "Scholar - London University", living with his widowed mother Jane whose occupation is listed as "Periodical Literature", and his older sister Sophia age 22 who is a teacher. Jane's sister Sarah age 48 is also a teacher.

Sinnett married his wife Patience in 1870, probably in the London area. He is listed in the 1871 England Census at age 31, as a Journalist, born in Middlesex. His wife Patience is 27, and her mother Clarissa Edenson a "Landowner", is living with them.

By 1879, Sinnett had moved to India where he was "... the Editor of The Pioneer, the leading English Daily of India..." Combined Chronology of The Mahatma Letters - Preface He relates in his book, The Occult World that: "...on the first occasion of my making Madame Blavatsky's acquaintance she became a guest at my home at Allahabad and remained there for six weeks..."

In 1880 Helena Blavatsky and Henry Steel Olcott visited the Sinnetts at their summer-home in Simla. The Mahatma letters, which generated the controversy that later helped lead to the split of the Theosophical Society, were mostly written to Sinnett or his wife, Patience.

By 1889, Sinnett was back in England, and asked Charles Webster Leadbeater to come back to England to tutor his son Percy and George Arundale. Leadbeater agreed and brought with him one of his pupils Curuppumullage Jinarajadasa. Using "astral clairvoyance" Leadbeater assisted William Scott-Elliot to write his book The Story of Atlantis, for which Sinnett wrote the preface.

Sinnett was later President of the London Lodge of the Society.

By 1901, Sinnett is listed as an author. His son Percy is also listed as an author and born in India.

• The Occult World, London 1881
• Esoteric Buddhism, London 1883
• Karma: A Novel, London: Chapman & Hall. 1885.
• The rationale of mesmerism, Boston 1892
• The Growth Of The Soul, London and Benares 1905
• Married by degrees; A play in 3 acts, London 1911
• In the next world: Actual narratives of personal experiences by some who have passed on, Theosophical Publishing Society, London 1914
• The spiritual Powers and the War, London 1915
• Unseen Aspects of the War; Two articles by A[lfred] P[ercy] Sinnett, London 1916
• The early days of theosophy in Europa, London 1922

Literature

• Autobiography of Alfred Percy Sinnett, Theosophical History Centre Publications, London 1986 ISBN 0-948753-02-1

Letters

• Helena P. Blavatsky: The letters of H. P. Blavatsky to A. P. Sinnett and other miscellaneous letters, London 1925
• A. Trevor Barker. The Mahatma Letters to A.P. Sinnett London 1926 (ISBN 1-55700-086-7)