The viral infection causes fever and joint pain, which can be severe, as well as headache, muscle pain, joint swelling and a rash, experts say.
Until now, the United States has only recorded cases of people coming back into the country with the virus after getting bitten while traveling, the Centers for Disease Control and Prevention said.
"The arrival of chikungunya virus, first in the tropical Americas and now in the United States, underscores the risks posed by this and other exotic pathogens," said Roger Nasci, chief of CDC?s Arboviral Diseases Branch.
The virus, pronounced chik-un-GUHN-ya, was first recognized in the Western Hemisphere seven months ago, and with cases mounting in the Caribbean, experts have warned it was only a matter of time before it made its way into the United States.
"The Centers for Disease Control and Prevention is working closely with the Florida Department of Health to investigate how the patient contracted the virus," said the health agency.
Authorities will "also monitor for additional locally acquired US cases in the coming weeks and months," it said in a statement.
The CDC did not release any further details about the Florida man.
There is no vaccine to prevent it and no medicine to treat it. However, the CDC says chikungunya is not often fatal and people usually recover within a week.
Symptoms are similar to dengue fever. Once a person is infected, he or she is likely to be protected against it in the future.
Since 2006, the United States has averaged 28 imported cases of chikungunya annually among people returning from countries in Asia, Africa, Europe, Central and South America and the Caribbean.