Interleukin-1β (IL-1β) is an important pro-inflammatory cytokine, which coordinates a variety of immune responses. It plays an important role in the host response to microbial invasion, tissue injury and immunological reactions including autoimmune disorders. IL-1β was the first interleukin to be characterised in fish and is mainly produced by blood monocytes and tissue macrophages. Till now no cytokines have been reported from green chromide (Etroplus suratensis), which is an important food and aquarium fish in South and South-East Asian countries. In the present study, IL-1β gene was cloned and characterised from E. suratensis (EsIL-1β) and the full-length cDNA sequence was deposited in the Genbank (Accession number. KT199302). The complete cDNA sequence of EsIL-1β is 1252 nt long with an open reading frame (ORF) of 741 bp encoding a putative protein of 246 aa. EsIL-1β mRNA transcript could be detected in all the twelve tissues tested with skin and spleen showing considerably higher expression in normal physiological condition. The immune modulatory activity of EsIL-1β against bacteria was studied by challenging the fish with a Gram-negative bacterium, Vibrio alginolyticus and Gram-positive bacterium, Staphylococcus aureus. To evaluate the antiviral function of EsIL-1β, the fishes were induced with viral imitator poly I:C and mRNA expression profile was determined in four tissues. EsIL-1β was constitutively expressed in all the tested tissues. In response to V. alginolyticus and poly I:C, Kidney showed the highest expression of EsIL-1β among the tissues tested. However, intestine showed the highest expression against S. aureus infection. These results revealed that IL-1β plays an important role in innate immune system against wide array of microbial invaders in E. suratensis.