BACKGROUND: Ticks are important ectoparasites in ruminants which cause economic losses in animal husbandry of Iran and worldwide. OBJECTIVES: This study was aimed to determine geographic distribution, frequency and species diversity of hard ticks in domestic ruminants in Ilam province, Iran. METHODS: A total of 445 domestic ruminants (139 cattle, 162 sheep, 144 goats) from 120 flocks of 30 villages in north and south parts of Ilam province were randomly selected and examined in summer 2015. The ixodid ticks were collected from body surface of examined animals and identified. RESULTS: Of all examined ruminants, 44.6% cattle, 51.23% sheep, and 52.08% goats were infested with a total number of 1209 unfed ixodid ticks. The highest prevalence of hard ticks was found in 2-3 year-old female cattle (15.55%), 1-2 year-old female sheep (19.75%) and less than 1 year-old female goats (17.36%) in the region. The highest prevalence was found in 2-3 year-old female cattle (37.1%), 1-2 year-old ewes (38.55%) and less than 1 year-old kids (33.33%). There was significant difference between prevalence and different age groups of infested sheep and cattle. Of 1209 collected ixodid ticks, tick indices (tick number per animal) were 6.1, 5.9 and 4.5 in cattle, sheep, and goats, respectively. The highest infestation in cattle (17 flocks, 14.1%), sheep (13 flocks, 10.8%) and goats (14 flocks, 11.6%) was respectively found in north, south and southern parts of the region. The highest tick aggregation was found for ears in cattle (31.13%), sheep (34.41%) and goats (28.9%). Of all examined ticks (1209), two genera including Hyalomma (37.62%) and Rhipicephalus (62.38%) with seven, seven, and six species in cattle, sheep, and goats were respectively identified. The predominant infesting ticks were R. sanguineus (22.16% in cattle) from north (11.31%) and H. anatolicum anatulicum (21.8% in sheep and 24.77% in goats) from south (15.49% and 13.42%) part of the province. CONCLUSIONS: The results revealed that species diversity and frequency of ixodid ticks were prevalent in domestic ruminants of different parts of Ilam province.