Gaynor attended high school in South Florida, Hollywood Hills. He went to college at North Texas State University, which is now known as University of North Texas, for their prestigious music program. After graduating, he worked as a producer of sports content for Sports News Network in the early 90’s, and worked for Criteria/Hit Factory Recording Studio in Miami from 1989-1995.
Gaynor was the rhythm guitarist and background vocalist for Matchbox 20 from 1995-2005 and performed on their first three albums. He left the band in 2005 while they were on hiatus. After leaving the band, Gaynor co-founded the Matchbox 20 Foundation, which has worked with Make-A-Wish Foundation, Special Olympics, Rock Against Cancer and Best Buddies and Art of Elysium in Los Angeles.
Gaynor currently lives in California. In 2012, he launched his new company Creationville and in September released his first book called This is Edgar Pingleton. On January 22, 2013 he appeared on Park City TV for the 2013 Sundance Film Festival. On March 11, 2013 Adam Gaynor released his first solo tracks, "Stuck" and "Float". On March 26, 2013 he appeared on Bravo TV's Millionaire Matchmaker.
- "Matchbox Twenty". Retrieved 2013-03-27.
- Creationville "Creationville". Retrieved 2013-03-26.
- "Ep 11: The Olympian and the Rock Star". 2013-03-26. Retrieved 2013-03-26.