A driver is sought after a boy was hit by a ute in Sydney's south-west yesterday.

At about 3.20pm, emergency services were called to Milperra Road in Revesby, between Edgar Street and Mons Road.

Paramedics found and treated a 12-year-old boy who had been hit by a car in the westbound lanes of the road.

He was taken to hospital in a serious but stable condition.

Police were told the boy was hit by the rear passenger side of the ute, which drove from the scene.

It's believed the driver may have been unaware of the incident.

Investigators have released images of a ute described as an orange or gold Nissan Navara with a hard-top canopy, silver bullbar, and black wheel hubs.

The driver of the car is urged to come forward.

Anybody with information or any relevant footage is urged to contact Crime Stoppers online or on 1800 333 000.