In 1990 Greer founded the Center for the Study of Extra-Terrestrial Intelligence (CSETI) 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. It also aims to grant amnesty to government whistleblowers willing to violate their security oaths by sharing insider knowledge about UFOs.

In May 2001, Greer held a press conference at the National Press Club in Washington, D.C featuring 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. Greer also produced Unacknowledged (2017), a more recent documentary in a similar vein.

Although Greer was initially seen as the ‘father of the modern Disclosure movement’ his credibility has fallen significantly over the years as he has become more known to make remarkable, unfounded claims and speculations while aggressively commercializing his projects.

Greer claimed to give a briefing to CIA director James Woolsey at a ‘dinner party’ which was later denied by Woolsey and the other attendees. Greer responded to the denial with his own claims, citing his wife’s account and the meeting was actually a briefing and not an informal gathering.

Greer hosted a press conference with credible UFO witnesses on Capitol Hill, but presented the work of others using his own name, causing significant controversy among those involved.

Greer has advertised private, paid UFO events at his farm in Virginia, where he offered to teach others the “nature of reality and the experience of higher states of consciousness” and what “extraterrestrial contact is really about.” Greer state the intent of the gathering was to create a historical record of events and designed to quickly get the truth out to the public, but had guests sign non-disclosure agreements and has yet to release anything resulting from such events. Greer has also advertised a specific methodology for establishing communication with extraterrestrials at similar paid events and several times claimed to have made contact with large craft, but never produced any tangible evidence of the fact.

Royce Myer, who writes at ufowatchdog.com, stated:

“Greer is quick with “the truth” and how the field of UFOlogy is often marginalized and subjected to ridicule while the faceless and nameless bad guys rush in to cover it all up. The reality here is one need not look any further than Greer (among others) for the real problem the UFO field is faced with: The charlatans , delusional personalities, and outright sensationalists who are taking center stage with their completely unfounded and often times exaggerated claims, citing of anonymous sources, and offering of not a shred of tangible evidence as to those claims.”