Doing so lets the animals live in restricted housing, accompany their owners into restaurants and fly free in airline cabins rather than in cargo holds, the South Florida Sun-Sentinel reported.
"I don't want to say it's a scam, but it's a scam," said Nick Kutsukos, 72. He runs the Elite K9 Academy in Jupiter and has trained service dogs for 40 years.
Those who would fraudulently pass their animals off as service providers often turn to the Internet, where it is possible to purchase specially marked vests or collars identifying their pet as a service animal.
"There is no certification required, so there's no such thing as a legitimate [document]," said Toni Eames, president of the Michigan-based International Association of Assistance Dog Partners.
"Anyone who sells you a certification is a scammer," said Eames, who is blind and has a guide dog.
Kutsukos, who has a service dog to help with his seizures, said the fake certifications "make it difficult for people with legitimate service dogs to do things."
Fraudulently passing an animal off as a service animal is against the law.
"If you portray yourself as disabled, or your pet as a service animal, the minute you go out in public you're committing a crime," said Ken Lyons, director of Orlando-based Service Dogs of Florida. "It's felony fraud."