Kimberly Barnes, of Lakeland, Fla., is suing Urban Air Adventure Park, also in Lakeland.
"I didn't realize how bad it really was, seeing and knowing it was my little boy," said Barnes. "It was just, it killed me, it killed me inside, it was the worst thing I could ever watch in my life."
According to the lawsuit, filed on Monday, Barnes claims her boy fell 20 feet onto a cement floor because employees failed to check or properly secure the harness before the ride.
The child spent five days in the hospital with a head injury, broken bones and a collapsed lung.
ABC News reached out to Urban Air for comment, but didn't immediately hear back.
ABC News contributed to this report.