The dognapping happened when the victim, a South San Francisco resident, was walking near Baden Avenue at about 11:15 a.m., police said.
A man approached the victim and forcibly removed her dog, a dark brown Chihuahua and Pomeranian mix, from its leash. He pushed the victim several times and ran away with the dog, police said.
The suspect was last seen running west in the 800 block of Second Lane. He was described as an Asian or Hispanic man approximately 35 years old, who was last seen wearing a blue colored shirt and baseball hat.
No arrests have been made. Anyone with information is asked to contact South San Francisco police at (650) 877-8900.