The boy's sister also fell through the ice on the pond in Clermont County east of Cincinnati on Sunday, but she was rescued and is expected to recover.
A dive team recovered the boy's body. He was pronounced dead at a hospital.
The property's owner, Landon Wiliams, says he told three children to get off the ice, and the brother and sister broke through as they were leaving.
Williams says he used an electrical extension cord to help pull the girl to safety. But the girl's brother went underwater as rescue crews arrived.
Their names haven't been released.