A baby boy is fighting for life after being pulled unconscious from a backyard pool in Sydney’s south-west.

Emergency services were called to a home on Lockheed Street in Raby about 7.30pm on Wednesday.

They found a 20-month-old boy who had been pulled from the water “unconscious and unresponsive”.

Know the news with the 7NEWS app: Download today

He was treated at the scene by NSW Ambulance paramedics before being taken to The Children’s Hospital at Westmead.

The boy remains in a critical condition, police said on Thursday morning.

“A crime scene has been established,” police said in a statement.

“Investigations into the circumstances surrounding the incident continue; however, the incident is not being treated as suspicious.”