The eukaryotic initiation factor 2 alpha subunit (eIF2α) is a key translation regulator that plays an important role in different cellular pressures and stimuli, including virus infection. In the present study, an eIF2α homolog (EceIF2α) from the orange-spotted grouper (Epinephelus coioides) was cloned and its roles during fish viral infection were characterized. EceIF2α encodes a putative protein of 315 amino acid residues, and shares a high degree of similarity with eIF2αs from other species. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that EceIF2α was distributed in all examined tissues. Both of the expression levels of EceIF2α in the spleen and head kidney of E. coioides were up-regulated when challenged with polyinosine-polycytidylic acid (poly[I:C]). EceIF2α was abundantly distributed in both the cytoplasm and nucleus in grouper spleen (GS) cells. Over-expression of EceIF2α improved the expression of red-spotted grouper nervous necrosis virus (RGNNV) genes in GS cells. In addition, EceIF2α depressed the activation of NK-κB and IFN-β. Furthermore, dephosphorylation inhibitor treatment led to a significant decrease of RGNNV gene transcription. Taken together, these results suggest that EceIF2α might be involved in the fish immune response to virus challenge.