Salmonella remains one of the most prevalent zoonoses worldwide. Although salmonellosis is commonly associated with the consumption of contaminated food, it has been estimated that up to 11% of Salmonella infections overall are acquired from direct or indirect contact with animals, including reptiles. In 2016, an outbreak of Salmonella Enteritidis involving multiple cases, especially children, associated with reptile contact and contaminated feeder mice was reported in the United Kingdom. The aim of this study was to investigate Salmonella external and internal contamination of stored commercial frozen feeder mice used to feed reptiles and obtained from the same supplier involved in the outbreak. In this study a total of 295 mice were tested (60 pinkies, 60 fuzzies, 60 small, 60 large, and 55 extra large). In this study, both external (integument) and internal (selected organs) contamination were evaluated. Salmonella Enteritidis PT8 and PT13 were isolated from 28.8% (n = 17) of the 59 batches tested, with the exception of the large mice category. Positive mice were mostly contaminated externally (92.3% vs. 26.9% for carcass wash and viscera, respectively). All isolates were sensitive to all 16 antimicrobials tested. The high level of external contamination of the rodent carcasses might have played a role in the human outbreak in 2016. Reptile owner management of the rodent carcasses at home could be an important source of salmonellosis outbreaks. Collaboration among public health officials, pet industry, veterinarians, and reptile owners is needed to help prevent the risk of salmonellosis associated with animal-based food intended for reptiles.