Additionally, Gay has returned the silver medal he won in the men's 400-meter relay at the 2012 London Olympics.
The 31-year-old Gay's one-year ban began on June 23, 2013, the day his sample was collected at the USA Outdoor Track & Field Championships. He accepted a loss of results dating back to July 15, 2012.
"Upon receiving notification of his positive tests from USADA, Gay voluntarily removed himself from all competition prior to the 2013 World Championships and has not competed since that time," USADA said in a release.
According to the release, Gay could have been suspended for two years for his first doping offense but received a reduction because of his substantial assistance into the investigation of his case.
"We appreciate Tyson doing the right thing by immediately withdrawing from competition once he was notified, accepting responsibility for his decisions, and fully and truthfully cooperating with us in our ongoing investigation into the circumstances surrounding his case," said USADA CEO Travis T. Tygart.
Gay's suspension is subject to appeal by the IAAF and the World Anti-Doping Agency.
The American record holder in the 100-meter dash admitted last July he had failed an out-of-competition doping test.