According to police in Concord, California, the 11-week-old pup named Max was taken from the garage of his owner's house on Saturday.
The San Francisco Chronicle reported Max belongs to a nurse.
Surveillance camera images posted Monday night by police showed the pup, who appears to be a Malinois, being picked up by a person on a bicycle.
The person was last seen wearing a green hooded jacket, a mask over the face, and blue medical gloves. The person was also sporting jeans and grey shoes, possibly New Balance brand.