YouTube video shows two men entering the store in South Pasadena. One is the lookout while the other picks up the puppy and walks out.
The 6-month-old dog is a puggle, a pug-beagle crossbreed, worth about $1,000. Investigators said the dog is micro-chipped and was registered as stolen.
Authorities said they arrested 53-year-old Jesus Medina of Los Angeles.