Mark Powell, 49, was arrested Thursday when he turned himself in to Hamden police, The Hartford Courant reported.
The 22-year-old woman, who had fallen and knocked herself unconscious at a holiday party, told police she came to while being taken to Yale-New Haven Hospital in an American Medical Response ambulance and found herself being attacked.
The woman told police she couldn't move because she was strapped to a stretcher.
Police Capt. Ronald Smith said she told police she waited three days to report the attack because she was embarrassed and afraid, CNN reported.
Powell is charged with first-degree sexual assault and first-degree unlawful restraint. He is free after posting $25,000 bail and is to be arraigned Jan. 19 in Superior Court in Meriden.
"His alleged actions are not reflective of our dedicated paramedics and [emergency medical technicians], who hold themselves to the highest standards of professional conduct," Charles Babson, general manager for American Medical Response, said.