Signal transducer and activators of transcription (STAT) gene, suppressors of cytokine signaling (SOCS) has been isolated from kuruma shrimp, Marsupenaeus japonicus and characterized. The kuruma shrimp STAT (MjSTAT) cDNA was composed of 2901 bp consisting of 801 amino acid residues which includes a protein interaction domain, all alpha domain, DNA binding domain and SH2 domain. Homology analysis of MjSTAT showed 94.1% and 34.0% identities with Penaeus monodon STAT (PmSTAT) and Drosophila melanogaster STAT92E (DmSTAT), respectively. The kuruma shrimp SOCS (MjSOCS) cDNA was composed of 1675 bp consisting of 342 amino acid residues including a SH2 domain and C-terminal SOCS domain. Homology analysis of MjSOCS showed 52.6% and 21.3% identities with Chinese mitten crab (Eriocheir sinensis) SOCS2 and fruit fly (D. melanogaster) SOCS44A, respectively. The MjSTAT and MjSOCS genes are constitutively expressed in the muscle, stomach, brain and gill of kuruma shrimp. In lymphoid organ cells, an enhanced expression of both MjSTAT and MjSOCS genes are observed following stimulation with peptidoglycan and polycytidylic acid. These observations suggest that MjSTAT and MjSOCS might play a major role in the innate immune defense of kuruma shrimp. The discovery of JAK/STAT signaling pathway in shrimp will allow a complete and concrete understanding of shrimp cytokine signaling. © 2012 Elsevier Ltd.