Lice are small wingless insects in the order Phthiraptera. Historically, the chewing louse Heterodoxus spiniger (Enderlein) was described from marsupials to the domestic dog (Canis lupus familiaris L.). Clinical manifestations of infestations by chewing lice are characterized by intense irritation and inflammation of the skin. We found six of 337 domiciled dogs from Tabasco State, Southeastern Mexico infested by chewing lice. Dogs were systematically examined, and ectoparasites were removed using a fine-toothed comb. Lice were deposited on a white sheet of paper and placed into plastic containers. The dog houses sampled were typically small and built of cement, and most inhabitants lived in vulnerable conditions. This is the first record of H. spiniger and the dog biting louse, Trichodectes canis (De Geer), infesting domestic dogs in Mexico. H. spiniger was present in the six dogs infested by lice, and T. canis co-infested one of them. Therefore, six infested dogs (100%) were positive for H. spiniger and one (17%) for T. canis. The importance of this report is that both ectoparasites are recognized as vectors of zoonotic diseases. Further studies are needed to clarify lice distribution, prevalence, and vectorial importance of neglected parasitic infections in Southeast Mexico.