The former neighbourhood watch volunteer told Florida TV station WOFL that he had just got the gun back from the US Justice Department, which took it after he was acquitted in Trayvon’s 2012 shooting death.
Mr Zimmerman told the station: “I thought it’s time to move past the firearm. And if I sell it and it sells, I move past it. Otherwise, it’s going in a safe for my grandkids and never to be used or seen again.”
The auction listing on GunBroker.com describes the gun as a 9 mm Kel-Tec PF-9 pistol. The auction began late last night with bidding starting at $5,000.
The listing also says that a portion of the proceeds will go towards fighting against violence by the Black Lives Matter movement against law enforcement, combatting anti-gun rhetoric of Democratic presidential candidate Hillary Clinton, and ending the career of Angela Corey, who led the prosecution against Mr Zimmerman.
When asked what he thought of people who would be opposed to auctioning the gun, he said: “They’re not going to be bidding on it, so I couldn’t care less about them.”
Mr Zimmerman has said he was defending himself when he shot and killed Trayvon, an unarmed black 17-year-old.
Mr Zimmerman said he has received death threats but has decided not to cower.
“I’m a free American,” he said. “I can do what I want with my possessions.”