The National Ocean Service made the announcement in response to enquiries from the public, prompted by a TV show on the mythical half-woman, half-fish.
It is reported that some viewers may have mistaken the programme for a documentary.
“No evidence of aquatic humanoids has ever been found,” the service wrote in an online post.
The Discovery Channel’s Animal Planet network screened Mermaids: The Body Found in May.
The channel has since conceded that some viewers believed the fictional show was a science education programme.
National Ocean Service spokeswoman Carol Kavanagh told the BBC that at least two people had written to the agency asking about mermaids.
Whoever said Americans were dumb?
