A woman has been charged after trying to steal a Chihuahua puppy at gunpoint, police say.

The 26-year-old woman went to a house on Perkins Avenue, Kellyville, in Sydney’s northwest, at 11.30am yesterday with an appointment to buy a puppy.

She allegedly produced a gun and demanded the puppy.

Police say the woman was restrained by the residents, including an off-duty policeman, and had her firearm seized.

Officers arrived and arrested the woman, who was carrying a replica Glock pistol, and charged her with armed robbery and possession of a prohibited weapon.

She will appear in Parramatta Local Court on October 15.