Hartmann was an associate of Helena Blavatsky and was Chairman of the Board of Control of the Theosophical Society Adyar.^[1] He collaborated with the mystic Carl Kellner. He published the journals Lotusblüthen (1893-1900) and Neue Lotusblüten (1908-1913). He wrote articles on yoga and popularized the subject within Germany.^[1]

He has been described as "one of the most important theosophical writers of his time".^[1] His works include several books on esoteric studies and biographies of Jakob Böhme and Paracelsus. He translated the Bhagavad Gita into German and was the editor of the journal Lotusblüten. He was at one time a co-worker of Helena Blavatsky at Adyar. In 1896 he founded a German Theosophical Society. He also supported the Guido-von-List-Society (Guido-von-List-Gesellschaft).

According to Theodor Reuss he was one of the original founders of the magical order that would later be known as Ordo Templi Orientis, along with Reuss and Carl Kellner.

• Magic: White and Black (London, 1886)
• The Life of Jehoshua, the Prophet of Nazareth
• The Principles of Astrological Geomancy
• Correlation of Spiritual Forces
• With the Adepts: An Adventure Among the Rosicrucians
• Life and the Doctrines of Philippus Theophrastus Bombast of Hohenheim Known as Paracelsus (1887)
• In the Pronaos of the Temple of Wisdom Containing the History of the True and the False Rosicrucians
• Alchemy and Astrology
• Metafisica Medicina y Sanacion
• Philosophy and Theosophy
• The Four Pillars of Occult Medicine
• The Life and Doctrines of Jacob Boehme (1891)
• An Adventure Among the Rosicrucians: A Student of Occultism
• Among the Adepts: The Brotherhood of the Golden and Rosy Cross and Their Occult and Mysterious Powers
• To Will, to Dare and to Be Silent in Magic
• Occult Science in Medicine (1893)
• The Talking Image of Urur (New York, 1890)

• Christianity and Theosophy
• Theosophists as fiction writers
• Buried Alive (1895)

• The Life and the Doctrines of Paracelsus, by Franz Hartmann
• The Life and the Doctrines of Jacob Boehme, by Franz Hartmann
• In The Pronaos of the Temple of Wisdom Containing the History of the True and the False Rosicrucians With an Introduction into the Mysteries of the Hermetic Philosophy by Franz Hartmann
• Magic, White and Black or The Science of Finite and Infinite Life Containing Practical Hints for Students of Occultism by Franz Hartmann Third Edition Fourth Edition Fourth American Edition Fifth American Edition Eighth American Edition
• Occult Science in Medicine by Franz Hartmann
• Personal Christianity: A Science: The Doctrines of Jacob Boehme, The God-Taught Philosopher With an Introduction and Notes by Franz Hartmann
• The Life of Jehoshua, the Prophet of Nazareth: An Occult Study and a Key to the Bible, Containing the History of an Initiate by Franz Hartmann
• The Life of Philippus Theophrastus Bombast of Hohenheim Known by the Name of Paracelsus and The Substance of His Teachings by Franz Hartmann
• The Principles of Astrological Geomancy, The Art of Divining by Punctuation According to Cornelius Agrippa and Others by Franz Hartmann
• With the Adepts: An Adventure Among the Rosicrucians by Franz Hartmann First Edition Second Edition
• Contents of Lotusblüten 1893-1900
• Contents of Lotusblüten 1908-1914
• Memorable Recollections from the life of the author of the "Lotusblüten".
• The Life of Jehoshua, the prophet of Nazareth - full text
• Digital edition of "Beitrag zur Litteratur über die Wirkung des Chloroforms" by the University and State Library Düsseldorf