Although the biology and ecology of the arthropod vectors are different, some factors, such as global warming, the increasing abundance of mosquitoes, the movement of domestic hosts, and the abundance of wild reservoirs, can act as favourable factors for the distribution of infections. The aim of this study was to determine the prevalence of Dirofilaria immitis infection in shepherd dogs living in the high altitude of mountainous area (i.e.1200 meters above the sea level). The study group was comprised of 160 shepherd dogs living in 4 mountainous regions (Targavar, Margavar, Kolshin and Hovarchin) of west Azerbaijan where continuous movement of sheep and goat flocks resulted to have a little information about shepherd dogs in these regions. Additionally, arduous pathways have made impossible any access by car to some territories of these areas. The dogs were mostly mixed raced with different ages (from 1 to 10 years) and sexes (male = 136, female = 24). Blood samples were collected from cephalic vein. Direct thin and thick blood smears and modified knott’s technique were used for detecting D.immitis microfilariae and other blood parasites. The results indicated that 40 (25 %) of dogs were infected with D. immitis microfilariae. In examination of the dogs, no severe life threatening feature of the disease was diagnosed. There were no significant differences (P > 0.05) of Dirrofilaria infection among gender, age groups and geographical areas. High prevalence of asymptomatic Dirrofilariasis in shepherd dogs in this area highlights the need of controlling and preventive programs.