MicroRNAs (miRNAs), the small non-coding RNAs, play a pivotal role in post-transcriptional gene regulation in various cellular processes. However, the miRNA function in shrimp antiviral response is not clearly understood. This research aims to uncover the function of pmo-miR-315, a white spot syndrome virus (WSSV)-responsive miRNAs identified from hemocytes during WSSV infection. The expression of the predicted pmo-miR-315 target mRNA, a novel gene called , was negatively correlated with that of the pmo-miR-315. Furthermore, the luciferase assay indicated that the pmo-miR-315 directly interacted with the target site in suggesting the regulatory role of pmo-miR-315 on gene expression. Introducing the pmo-miR-315 into the WSSV-infected shrimp caused the reduction of the transcript level and, hence, the PO activity activated by the PPAE3 whereas the WSSV copy number in the shrimp hemocytes was increased. Taken together, our findings state a crucial role of pmo-miR-315 in attenuating proPO activation via gene suppression and facilitating the WSSV propagation in shrimp WSSV infection.