In this study, totally 180 stray and domestic dogs in 6 districts of Ulaanbaatar city, Mongolia were tested for infection with microfilariae. Microfilariae were found in peripheral blood smears of 2 out of 180 (1.1%) tested dogs. In contrast, out of tested dogs, 2.2% were found to be infected by microfilariae by the Knott’s method. Higher prevalence was found in stray dogs (10%) than in domestic dogs.