Transforming growth factor β (TGFβ) is an immunomodulatory cytokine which is able to modulate the host immune response eliciting an inefficient response against pathogens. In this sense, the role of this cytokine in porcine reproductive and respiratory syndrome (PRRS) has been poorly studied and the reported results are contradictory. Thus, in the present study, the expression of TGFβ was analysed both at tissue (lymphoid organs and lung) and serum level to study its correlation with the expression of PRRS virus (PRRSV). To carry out this study, 32 pigs were inoculated with the European PRRSV field isolate 2982 and sequentially killed from 0dpi to the end of the study (24dpi). Blood and tissue samples were collected to determine the expression of PRRSV and TGFβ. PRRSV was detected in inoculated animals from 3dpi until the end of the study, however TGFβ was not detected in sera from inoculated animals. Contrary, an increase of TGFβ antigen was observed both in the lymphoid organs and in the lung of PRRSV-inoculated pigs when compared with control group. Since TGFβ play a role as an immunomodulatory cytokine of the immune response and also in the differentiation of regulatory T cells (Tregs), the upregulation of the TGFβ at tissue level may play a role in the impairment of the host immune response observed during PRRS, being observed a significant correlation between PRRSV and TGFβ expression at lung level.