Bovine ISG15 (bISG15) is an interferon inducible ubiquitin-like protein that is responsible for the establishment of early pregnancy in ruminant, understanding the properties of bISG15 capable of being inducible in fetal bovine lung (FBL) cells upon infection of bovine immunodeficiency virus (BIV) is of significant importance. In this study, we investigated the expression of bISG15 in poly I:C treated FBL cells. The increased expression of bISG15 was observed, and the inhibition of BIV replication was also detected in FBL cells. Elimination of bISG15 expression by small interfering RNA reversed the bISG15 mediated inhibition of BIV replication. These findings demonstrate that bISG15 plays an important role in inhibition of the BIV replication in FBL cells. Furthermore, real-time PCR and western blot assay revealed that bISG15's expression can also be induced in BIV infected FBL cells. Taken together, bISG15 is an antiviral and inducible protein in BIV infected FBL cells.