Background: BIV is a well-known bovine immunosuppressive cause, but its pathogenesis has not been well characterized. In recent years, it has been hypothesized that infection with BIV might predispose cattle to be infected by other agents. OBJECTIVE: This study was performed to investigate of BIV and Brucella co-infection so that in the future more studies will be done on the issue of predisposing cattle to other microorganisms like Brucella after BIV infection. METHODS: Blood samples were collected from a total of 2290 cattle in Iran (490 and 1800 cattle in non-industrial and industrial dairy farms, respectively from Isfahan and Chaharmahal and Bakhtiari provinces). The BIV-positive animals were detected by Lab-ELISA and nested PCR tests. RESULTS: In this study, the overall prevalence of BIV in Iran was 1.61% (4.5% and 0.83% in non-industrial and industrial dairy farms, respectively). CONCLUSIONS: There was a statistically significant relationship between BIV status and Brucella infection using Chi square and Pearson’s correlation coefficient test for all of the samples (p=0.0001, r=0.24), samples from Chaharmahal and Bakhtiari (p=0.044, r=0.13) and from industrial farms in Isfahan (p=0.001, r=0.074).