A 15-year-old girl has been sexually assaulted by two males in Sydney's west as she walked home.

The girl is alleged to have been assaulted by the males at Cowper Street Park, Quakers Hill, about 10.30pm yesterday.

Police said today they were contacted about 10.45pm about the incident.

They had spoken to the girl but she was unable to provide further details and she was taken to hospital to be examined.