The incident happened in Sandown Close, Hounslow at 1.10pm yesterday (August 3).
Officers and London Ambulance Service crews attended and found a boy injured.
He was taken to hospital for treatment where his condition was assessed as non life threatening.
No arrests have been made as police enquiries continue.
A spokesperson for Metropolitan Police said: “At 1.10pm on Sunday, August 3 officers and the London Ambulance Service responded to reports of a fall from height from an address on Sandown Close, Hounslow.
“A three-year-old boy was taken to hospital – his condition has not been deemed life-changing or life-threatening.
“He remains in hospital.
“There is no criminal investigation at this stage and no arrests have been made.”
