He appeared in Fox TV's 2001 "documentary" Conspiracy Theory: Did We Land on the Moon?, which re-ignited public interest in the Moon landing hoax claims. His interview during the show appears to support the hoax claim; later, it turned out that he had been quoted out of context.
In his later years, he became an advocate of the free energy suppression conspiracy theory. He believed that we have been visited by aliens and claimed to have detailed knowledge of their technology, something to do with toroids.
O'Leary relocated to Vilcabamba, Ecuador in 2008 to found the Montesuenos retreat together with his wife, artist Meredith Miller. He died there of intestinal cancer in 2010.
- O'Leary, Brian (1970). The making of an ex-astronaut. Houghton Mifflin. pp. 243. ASIN B0006C0CT6.
- O'Leary, Brian (1981). The fertile stars. Everest House. pp. 132. ISBN 978-0896960794.
- O'Leary, Brian (1989). Exploring Inner and Outer Space: A Scientist's Perspective on Personal and Planetary Transformation. North Atlantic Books. pp. 182. ISBN 978-1556430695.
- O'Leary, Brian (1993). The Second Coming of Science. North Atlantic Books. pp. 151. ISBN 978-1556431524.
- O'Leary, Brian (1996). Miracle in the Void: Free Energy, Ufos and Other Scientific Revelations. Kamapua's Pr. pp. 278. ISBN 978-0964782600.
- O'Leary, Brian (2009). The Energy Solution Revolution: A Socio-Political Journey Through the Tangled World of Free and Clean Energy, Its Promise, Its Suppression and Its Logical Necessity for Our Survival. Bridger House Publications. pp. 272. ISBN 978-0979917646.