The Los Angeles County Sheriff's Office said security video from Ace Smoke Shop in Altadena depicts two hooded men entering the store with a rifle at about 7:30 p.m. July 7 and demanding money, the Los Angeles Times reported Tuesday.
The video shows the store owner begin to place money into a backpack worn by one of the robbers while his Chihuahua starts barking loudly and forcefully at the men.
Investigators said the robbers were apparently spooked by the dog and fled the store with less money than they could have obtained from the store owner.
The video depicts the Chihuahua follow the men from the store and chase them down the street.
No one was injured in the incident, deputies said.
The sheriff's office said it is searching for the suspects, described as male Latinos.