Bluetongue (BT) is an important disease of ruminant livestock that is currently emerging in previously unaffected regions, most notably extensive portions of Europe. The epidemiology of BT virus (BTV) infection is poorly defined in much of the world, including extensive portions of Asia and the Middle East. Thus, the objective of this study was to describe the distribution and seroprevalence of BTV infection of sheep in West Azerbaijan Province of Iran, and to identify demographic and climatological factors associated with exposure of these sheep to BTV infection. BTV infection was widespread in the province as 400 of 1153 (34.7%) of the sheep sera evaluated contained antibodies to BTV, as determined by competitive ELISA, and 172 of 184 flocks included BTV seropositive sheep (93.5%). Multivariable logistic analyses failed to identify specific demographic or animal management practices that were predictive of BTV serological status of the sheep flocks. The virus serotypes and vector insects that occur within the region remain unknown.