A man is fighting for his life after being bashed in the head in his home in western Sydney yesterday evening, police say.

The 55-year-old was found lying on the lounge room floor of his home on Livingston Avenue in Dharruk by a family member about 7pm, Chief Inspector Bill Pearce of Mt Druitt Local Area Command said.

Chief Inspector Pearce said the man's injuries were "very serious" and that he may have been hit in the head with an iron bar.

"There's no evidence there was a forced entry to the premises," he said, adding that investigators did not yet know if the attack was carried out by one or more assailants.

Police also did not have any information that suggested the attack was linked to previous incidents, Chief Inspector Pearce said.

The man was taken to Westmead Hospital and was in intensive care in a critical but stable condition this morning, a hospital spokeswoman said.

Chief Inspector Pearce said detectives from other stations were assisting in the investigation and witnesses were being interviewed throughout today.

Police appealed for anyone with information to phone Crime Stoppers on 1800 333 000.