Reunion for child found wandering Sydney

A small child found wandering the streets of western Sydney alone during the night will be reunited with his parents.

Police say the child, aged three or four, was found knocking on doors in Fairfield's Francis Street about 4.15am on Sunday.

The toddler's long black hair initially had police thinking the child was a girl, but the mistake was realised and the boy's family were found nearly five hours after he was first discovered by neighbours.

"The exact circumstances of how he went missing are still not clear," a NSW Police spokesman said, but no further police action is expected.

The boy had only made it a block away from his home.