The child was playing in the water with his aunt about 6 p.m. EDT Monday. He dove down to the bottom of the pool when he saw a toy stuck in the drain.
He got his arm got caught and although his aunt immediately dove in to rescue him, she couldn't get his hand out, the celebrity news website said Tuesday.
A maid and two men working in the house worked to free the boy, who was given CPR immediately and rushed to the hospital.
Usher was not at home at the time of the incident, but he arrived in time to ride in the ambulance with his son, TMZ said.
The boy remained hospitalized, but was expected to make a full recovery, the report said.
The boy is the older of Usher's two sons with his ex-wife Tameka Raymond.
Kile, Tameka's 11-year-old son from a previous relationship, died last year from injuries sustained during a personal watercraft accident.