Suppressor of cytokine signaling 1 (SOCS1) protein can inhibit the signal transduction triggered by some cytokines or hormones and thus are important in many physiological/pathological processes, including innate and adaptive immunity, inflammation, and development in mammals. However, there is sparse information about their structure, tissue expression, in birds, where their biological functions remain unknown. In this study, we cloned and characterized two genes (named and ) from chickens. is predicted to encode a 207-amino acid protein, which shares high amino acid sequence identity (64%–67%) with human and mouse SOCS1. Besides , a novel gene was also identified in chickens and other non-mammalian vertebrates including . Chicken is predicted to encode a 212-amino acid protein, which shares only 30%–32% amino acid sequence identity with human SOCS1 and cSOCS1a. RT-PCR assay revealed that both and are widely expressed in all chicken tissues. Using a luciferase reporter assay system, we further demonstrated that transient expression of and can significantly inhibit chicken growth hormone (GH)- or prolactin (PRL)-induced luciferase activities of Hep G2 cells expressing cGH receptor (or cPRL receptor), indicating that SOCS1a and SOCS1b proteins can negatively regulate GH/PRL signaling. Taken together, these data suggest that both cSOCS1a and cSOCS1b may function as negative regulators of cytokine/hormone actions, such as modulation of GH/PRL actions in chickens.