The suppressor of cytokine signaling 3 (SOCS3), as a negative regulator in inferferon (IFN) signaling pathways in mammals, has a vital role in immune systems. However, studies on the function of SOCS3 in lower vertebrates are limited. In this study, we identified SOCS3a and fish-specific SOCS3b gene in miiuy croaker. Sequence analysis results showed that SOCS3a and SOCS3b were evolutionarily conservative in fish. Expression analysis indicated that miiuy croaker SOCS3a and SOCS3b (mmSOCS3a and mmSOCS3b) were expressed in all of the tested miiuy croaker tissues, thus revealing the potential ability to perceive poly (I:C) stimulation. Further functional experiments showed that mmSOCS3a and mmSOCS3b could inhibit the IFNγ- and IFNα-induced ISRE reporter activation, respectively. Accordingly, the investigation of mmSOCS3a and mmSOCS3b can provide insights into fish SOCS3 and a basis for future research on the SOCS family of fish immune systems.