Interleukin 1β(IL-1β), the first interleukin to be characterized, plays a key role in regulating the immune response. In this study, we determined the c DNA and genomic DNA sequences of the IL-1β gene from the large yellow croaker, Larimichthys crocea. Phylogenetic analysis indicated that the IL-1β(Lc IL-1β) gene was most closely related to that of European seabass(Dicentrarchus labrax), sharing 67.8% amino acid identity. In healthy large yellow croaker, Lc IL-1β transcription was detected in all tested tissues, with the highest level found in the head kidney. Upon Vibrio alginolyticus infection, Lc IL-1β transcription in all tested tissues was significantly upregulated. Intraperitoneal injection of recombinant Lc IL-1β(r Lc IL-1β) improved the survival rate and reduced the tissue bacterial load after V. alginolyticus infection. In addition, r Lc IL-1β induced monocytes/macrophages(MO/MΦ) chemotaxis and increased phagocytosis and bactericidal activity in vitro. These results suggest that Lc IL-1β plays an important role in the large yellow croaker immune response against V. alginolyticus. The first interleukin to be characterized, plays a key role in regulating the immune response. In this study, we determined the DNA and genomic DNA sequences of the IL-1 β gene from the large yellow croaker, Larimichthys crocea. Phylogenetic analysis indicated that the IL-1β (Lc IL-1β) gene was most closely related to that of European seabass (Dicentrarchus labrax), sharing 67.8% amino acid identity. In healthy large yellow croaker, Lc IL-1β transcription was detected in all tested tissues, with the highest level found in the head kidney. Upon Vibrio alginolyticus infection, Lc IL-1β transcription in all tested tissues was significantly upregulated. Intraperitoneal injection of recombinant Lc IL-1β (r Lc IL- improved the survival rate and reduced the tissue bacterial load after V. alginolyticus infection. In addition, r Lc IL-1β induced monocytes / macrophages (MO / MΦ) chemotaxis and increased phagocytosis and bactericidal activity in vitro. These results suggests that Lc IL-1β plays an important role in the large yellow croaker immune response against V. alginolyticus.