Green first began investigating Sasquatch sightings and track finds in 1957 after meeting René Dahinden and the two researchers collaborated in interviewing witnesses and sharing information of alleged sightings. A year later Green was shown a series of 15" tracks crossing a sandbar beside Bluff Creek in California so deeply impressed as to indicate a weight many times that of any potential hoaxer. He has been trying ever since to establish what it is that makes the tracks. Green is also the only surviving person to have investigated the original Sasquatch tracks reported in Bluff Creek, California in the summer of 1958.

As a renowned authority in the field, Green has appeared as a keynote speaker at all three of the major scientific Sasquatch symposia held so far. Green has authored several Sasquatch books, including Sasquatch: The Apes Among Us, still widely regarded by many as the single best book yet written on the subject. It has recently been re-issued, along with an updated combination of the two earlier books and is entitled The Best of Sasquatch Bigfoot.

Green currently resides in Harrison Hot Springs, British Columbia.