A baby has been found alone in his capsule on a western Sydney street.

The boy was found on Joseph Street, Lidcombe at 3:15am today.

It's believed he had been lying in the street for over an hour before being found.

Shortly after, police were called to Lidcombe Railway Station responding to reports of a couple arguing.

It was established that the man and woman were the parents of the baby boy.

According to reports, witnesses noted the pair didn't appear concerned about their baby nor did they ask after his welfare.

The couple was taken to Auburn Police Station.

The baby was taken to The Children's Hospital Westmead where he was treated for a cold.