Ticks are important parasites because of their voracious blood-feeding activity, and being as vectors for various agents of diseases in both human and livestock. This study was conducted in a monthly schedule from October 2014 to December 2015, at 45 study sites in three regions bordering the Caspian Sea, according to the topography including hillside, plain and coastal areas in collecting ticks from the body of sheep. Alfa and Beta biodiversity indices were calculated and compared between the three areas under study. In this study, 1583 out of a total of 3904 inspected sheep (40.54%), were infested with ticks, and 2410 ticks were collected, out of which 36.5, 34.8 and 28.7% were related to the coastal, plain and hillside areas, respectively. The identified tick specimens belonged to 3 genera and 9 species including Hyalomma marginatum, Hyalomma anatulicum, Hyalomma asiaticum, Hyalomma excavatum, Rhipicephalus bursa, Rhipicephalus turanicus, Rhipicephalus sanguineus, Haemaphysalis parva and Haemaphysalis punctata. With regards to the seasonal variation, the highest and lowest tick infestation was recognized in spring and winter, respectively. Monthly activity of ticks on sheep revealed that Hy. marginatum exhibited two peaks of activity in June and July in the coastal and plain regions, but in the hillside area these peaks for Rh. turanicus occurred in August. Differences in species richness has been proved significantly in Margalef index in the study area (P
