Canine hepatozoonosis is a tick-borne disease caused by Hepatozoon canis (James, 1905) and Hepatozoon americanum (Vincent-Johnson, 1997). The disease has been reported infrequently in Mexico. The aim of this report was to describe haemato-biochemical changes and confirm diagnosis by molecular-based methods of clinical infection by H. canis in a dog. A 9-year-old female, boxer dog, Canis familiaris (Linnaeus, 1758), was taken to a veterinary clinic at Colima, Mexico. The dog showed depression and more than 2 weeks of gradual weight loss without decreased appetite. Rhipicephalus sanguineus (Latreille, 1806) ticks were found when the dog was physically examined. Blood samples were collected for smear, hematological, and biochemical analyses, and PCR assays. Hematological analysis revealed an apparently non-regenerative normochromic normocytic moderate anemia, mild thrombocytopenia, left shift without neutrophilia, and mild lymphopenia associated with possible stress. Biochemical analysis showed hyperbilirubinemia, hyperamylasemia, hypoalbuminemia, hyperglobulinemia, increased ALT, and hypocalcemia. Microscopic examination of Diff-Quick-stained blood smears showed capsule-shaped structures consistent with gametocytes of Hepatozoon sp. Clinical history, hematological changes, and molecular assays described in the report confirmed the first case of canine hepatozoonosis caused by H. canis in the Pacific region of Mexico.