Looks can be deceiving. And costly, too.

That’s what a Queens-based security company learned after one of its guards blocked a man with vision problems and HIV from entering a public building in 2009 with his service dog — even though he had a permit for the pooch.

Charles Romo Jr., 47, of Crown Heights, Brooklyn, was awarded more than $35,000 last month after an administrative law judge ruled that ISS Action Security — a state vendor — discriminated against Romo.

ISS did not return calls for comment.