Prosecutors said he was a wannabe cop who tracked down the teenager and shot him without justification in the U.S. town of Sanford.
Zimmerman said he shot Trayvon Martin in self-defence - and the jury agreed.
Outside the court supporters of Martin's family were outraged.
"How could you kill somebody and get off? It's a stark felony."
"He racially profiled Trayvon, he stalked him, and he murdered him."
"What we want is responsible use when someone feels that they have to use a gun to take a life. They have to be responsible in their use and we believe that this case all along was about boundaries and that George Zimmerman exceeded those boundaries."
Zimmerman's defence team was critical that he was even brought before a court.
DONALD WEST, ZIMMERMAN'S DEFENCE ATTORNEY:
"I think the prosecution of George Zimmerman was disgraceful. I am gratified by the jury's verdict, as happy as I am for George Zimmerman, I'm thrilled that this jury kept this tragedy from becoming a travesty."
The case became a nation-wide issue when Zimmerman remained free for more than six weeks after the shooting because police believed his version of events.
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