The US Justice Department said Sunday it would look into the case and consider whether to bring criminal civil rights charges against Zimmerman.
The department opened an investigation into the shooting last year but stepped aside so the state could conduct its own investigation.
"Experienced federal prosecutors will determine whether the evidence reveals a prosecutable violation of any of the limited federal criminal civil rights statutes within our jurisdiction," the statement said, according to The Associated Press.
The department added that it will determine "whether federal prosecution is appropriate in accordance with the department's policy governing successive federal prosecution following a state trial."
A jury found Zimmerman not guilty of second degree murder and manslaughter Saturday night after a highly publicized trial.
Zimmerman admitted to killing Martin that rainy night in February 2012 but claimed it was in self defense.
Civil rights groups including the NAACP and the American Civil Liberties Union called upon US Attorney General Eric Holder to look into the case.
"Those of us who are fathers, particularly of African-American boys, find it shockingly frightening," Hilary Shelton, director of the NAACP's Washington bureau said in a statement.
The message, he said, is, "Not only can we do this, we can get away with it."
If the Justice Department does open a federal civil rights case it will likely be a tough case to prove.
"There are several factual and legal hurdles that federal prosecutors would have to overcome," Alan Vinegrad, the former US Attorney in the Eastern District of New York, told AP.
"They'd have to show not only that the attack was unjustified, but that Mr. Zimmerman attacked Mr. Martin because of his race and because he was using a public facility, the street."
President Barack Obama said on Sunday that "a jury has spoken."
"I know this case has elicited strong passions. And in the wake of the verdict, I know those passions may be running even higher," Obama said.
But he asked the public to respect the Martin family's appeal for "calm reflection" in the case.