Greer was born in Charlotte, North Carolina in 1955. He claims to have seen an unidentified flying object at close range when he was about eight years old, which inspired his interest in ufology.
Greer was trained as a Transcendental Meditation Teacher and served as Director of a meditation organization. He completed his graduate work at East Tennessee State University James H. Quillen College of Medicine in 1987. He attended MAHEC University of North Carolina where he completed his internship in 1988 and received his Virginia medical license in 1989. That year he became a member of the Alpha Omega Alpha Honor Medical Society.
Greer founded the Center for the Study of Extra-Terrestrial Intelligence (CSETI) in 1990 to create a diplomatic and research-based initiative to contact extraterrestrial civilizations. In 1993, he founded the Disclosure Project, a nonprofit research project, whose goal is to disclose to the public the government's alleged knowledge of UFOs, extraterrestrial intelligence, and advanced Energy and propulsion systems. The Disclosure Project was founded in an effort to grant amnesty to government whistle-blowers willing to violate their security oaths by sharing insider knowledge about UFOs. Greer says he gave a briefing to CIA Director James Woolsey at a dinner party, although this was denied by Director Woolsey and attendees.
In October 1994, Greer appeared in Larry King's TV special The UFO Coverup? In 1995, Greer worked as a physician at the department of emergency Medicine at Caldwell Memorial Hospital, where he was chairman.
In 1997, Greer, along with other members of CSETI, including Apollo Astronaut Edgar Mitchell, made a presentation at a background briefing for members of Congress. In 1998, Greer gave up his career as an emergency room physician in favor of the Disclosure Project.
In May 2001, Greer held a press conference at the National Press Club in Washington, D.C. that featured 20 retired Air Force, Federal Aviation Administration and intelligence officers. According to a 2002 report in the Oregon Daily Emerald, Greer has gathered 120 hours of testimony from civilians and various government and military officials, including Astronaut Gordon Cooper and a brigadier general, on the topic of UFOs.
In 2013, Greer co-produced Sirius, a documentary detailing his work and hypotheses regarding extraterrestrial life, government cover-ups and close encounters of the fifth kind. The film was directed by Amardeep Kaleka and narrated by Thomas Jane, and covers Greer's 2006 book Hidden Truth, Forbidden Knowledge. The movie premiered on April 22, 2013, in Los Angeles, California, and features interviews from former government and military officials.
