A woman has been found dead inside a house that went up in flames in NSW.

Fire crews were called to terraces on Westbourne St at Petersham in Sydney’s inner west about 11.50pm on Friday night

Police evacuated neighbouring homes while firefighters worked to put out the blaze.

Know the news with the 7NEWS app: Download today

A body – believed to be that of an 82-year-old woman – was found inside the building.

She has not yet been formally identified.

A second occupant of the home – a 57-year-old man – was treated at the scene by paramedics for smoke inhalation and taken to hospital in a stable condition.

No one else was injured.

“Officers attached to Inner West Police Area Command have established a crime scene and commenced an investigation into the fire,” NSW Police said.

A report will be prepared for the coroner.

Anyone with any information has been urged to contact Crime Stoppers.