A woman has been stabbed while trying to break up a fight between her sons at a western Sydney home, police say.

Two brothers, 29 and 30, were brawling at a Granville home on Wednesday afternoon, threatening each other with furniture when the older man pulled a knife, police said.

Their 70-year-old mother tried to stop the fight but was stabbed in the left arm by her son, police said.

She was taken to Auburn Hospital for treatment.

Her sons were arrested and have been charged with assault offences.

Both were refused bail and are due before Parramatta Local Court on Thursday.