A female boxer named Precious was taken Friday afternoon from the Petland on Route 59 in Naperville, the store's owner said.
Adam Stachowiak said a man and two women came into the shop and asked to play with puppies, all small breeds.
A female employee brought 3-month-old Precious to the man in one of the store's playrooms. The women then began asking the employee and others questions about the dogs.
"They pulled all the employees to the back of the store," Stachowiak said, adding the man walked out the front doors with Precious about 5:15 p.m. The women followed less than a minute later.
The man was wearing a black shirt and sweatpants. One woman wore black pants and a pink shirt, and the other, a white sari, according to surveillance video.
Naperville police have received a report of a theft at the store, 720 S. Rte. 59, but the case has not been assigned an investigator, Cmdr. Raymond Adkins said Saturday afternoon.
Despite experimenting with security measures, the store generally sees the theft of a dog once a year, Stachowiak said.
"When (thieves) come in with a plan to do that, there's really not a lot of precautions we can take," he said.
The store tried holding onto customers' driver's licenses while they played with pets for two to three years, but that became difficult to manage, the owner said.
The most effective way to guard against theft is "really intense staff training," Stachowiak said.
In November 2013, a white Havanese puppy named Casper was taken from the store.
A Missouri woman charged in the case and in similar thefts in Bolingbrook and her home state turned herself in to police this March.
"It's just unfortunate that people think that's the only thing they can do to get a pet," Stachowiak said.
He has sent out a "lost pet" alert on Petkey.org and urged anyone with information about Precious to contact Naperville police.