Background: Canine babesiosis is a common and clinically significant tick-borne disease caused by obligate haematozoan parasites of the genus Babesia.Purpose: To report Babesia canis canis genotype A infection in a dog. Methods:A 2-year-old female Shih Tzu dog was submitted with the history of anorexia and depression for one week and no prior surgery. Fever, anorexia, depression and vomiting as well as mucosal pallor were noticed on physical examination. Microscopic examination of the Giemsa-stained blood smear disclosed large form of Babesia, and single to four pear-shaped merozoites within erythrocytes (RBCs). The specific primers were used for detecting Babesia canis. Results:The result of PCR was confirmed by 18S rRNA gene sequence analyzing and has been registered in GenBank under following accession numbers for Babesia canis canis (MW199108). The sequences were compared to those in GenBank, and alignments showed that the B. canis canis isolate belonged to genotype A.Conclusions: This is the first description of B. canis canis genotype A in dog from Iran.