Anaplasma phagocytophilum, the causative agent of equine granulocytic anaplasmosis, affects several species of wild and domesticated mammals, including horse, besides human. In Turkey, there were many reports on A. phagocytophilum circulation among cattles, sheep, dogs, mice, humans, except horses. In this study, we aimed to inquiry whether A. phagocytophilum were circulating among the horse population or not. For this purpose, 105 mare horse blood sera were examined for the presence of Anti-Anaplasma phagocytophilum IgG antibodies by IFAT. The seroprevalance rate of 8.57% horse sera were found to be positive. This was the first report about the presence of anti-A. phagocytophilum antibodies in horses in Turkey..