Police officers are calling on Tregear residents who may have witnessed a man climbing in the bedroom window of a 5-year-old boy to come forward and make a statement to help in the authorities' search, ninemsn.com.au reports.

A five-year-old boy, whose name has been withheld, was confirmed to have been indecently assaulted by a man who entered his family's house through his bedroom window on McMurdo Avenue, Tregear, about 3.20am (AEDT) on Sunday.

After the sexual assault, the man reportedly left the house through the same window.

Forensic specialists have examined the scene, and the boy was taken to Westmead Children's Hospital for medical examination.

Police are urging possible witnesses in the vicinity of McMurdo Avenue to contact Mount Druitt Police Station or Crime Stoppers on 1800 333 000.