House mice, Mus musculus, are reservoirs of zoonotic pathogens and parasites, but most consumers assume mice sold by pet stores are disease- and parasite free. We purchased 30 frozen mice from 15 pet stores in South Carolina and examined them for ectoparasites. All mice were infested with 1 or more of the following ectoparasites: unidentified Acaridae, Liponyssoides sanguineus, Myocoptes musculinus, Myobia musculi, Ornithonyssus bacoti, Polyplax serrata, or Radfordia affinis. Both L. sanguineus and O. bacoti are vectors of zoonotic pathogens. The presence of ectoparasites on commercially available mice implies that other pets could be infested with ectoparasites.