Jah-Nea Myles, 16 months, apparently slipped through the balcony railing and fell into the arms of Helen Beard.
Ms Beard, of Worksop, was at the pool at Orlando's Econo Lodge hotel when she saw the baby hanging from the railing and ran underneath, she said.
She held the child until emergency medical workers arrived.
The baby was taken to hospital, where medical staff said they saw no bruises or scratches and deemed her in good health.
An investigator with the Orange County sheriff's office described her as "playful" and said she was not crying.
Helena Myles, Jah-Nea's 20-year-old mother, told police her friend Dominique Holt had been watching the baby in the adjacent hotel room.
Ms Holt, 21, said she went to the bathroom about 2100 local time (0100 GMT), then heard screaming and saw the balcony door ajar.
She ran out onto the balcony and saw the baby in the arms of Ms Beard, from Nottinghamshire.
Ms Myles told Reuters: "She's perfectly fine. Not a scratch on her body.
"I'm thanking the Lord above right now for saving my child's life. I'm also thanking that lady because she was an angel sent from heaven."
Police said no criminal charges were pending.
Orlando is a popular destination for holidaymakers, with Walt Disney World and other tourist attractions.
A toddler who fell from the top floor of a four-storey Florida hotel has escaped injury after being caught by a British woman on holiday.