A security guard has been acquitted of all charges relating to the shooting of unarmed black teenager Trayvon Martin.
There were protests outside the courtroom as the all-women jury announced the unanimous verdict after 15-hour deliberation.
Zimmerman, who had pleaded self defence, stood impassively as the verdict was announced, Sky News reported.
The trial had kept America captivated, after the case first came to national attention because of the 44 days it took for Zimmerman to be arrested.
It sparked a fierce national debate about racial profiling in the United States, with celebrities including Jamie Foxx lending their support for Martin.
Martin, 17, was shot dead walking home in the gated community where he was staying after buying sweets and a drink.
Trayvon Martin supporters reacted with dismay to the verdict
Zimmerman's lawyers said Martin had attacked the older man, knocking him to the ground and banging his head against the pavement.
But prosecutors called him Zimmerman a liar, saying he had taken the law into his own hands.
There were overnight protests in a number of cities around the country, the BBC reported.
After the case, Zimmerman's lawyer, Mark O'Mara, told reporters: "Hopefully everyone will respect the jury's verdict."
Zimmerman would have to be careful of retribution, he said.
Another member of the defence team, Don West, said: "I'm thrilled that this jury kept this tragedy from becoming a travesty."