Chicken interleukin-3 (IL-3) is a hematopoietic growth factor produced by activated T cells that supports the proliferation and differentiation of hematopoietic progenitor cells, contributing to the development of myeloid lineage cells through activation of JAK/STAT and related signaling pathways. In avian species, IL-3 plays a role in regulating immune cell expansion, including macrophages, heterophils, and other innate immune populations that are critical for early host defense. In poultry health, IL-3 is relevant to immune responses against economically significant pathogens such as avian influenza virus, Newcastle disease virus, Salmonella, and Eimeria species, influencing inflammatory responses, vaccine responsiveness, and recovery from infection. Proper regulation of IL-3–mediated hematopoiesis is important for maintaining immune competence without promoting excessive inflammation that could impair growth and production efficiency. Beyond agricultural applications, chicken IL-3 contributes to avian immunology research and serves as a valuable model for studying evolutionary aspects of cytokine signaling and hematopoietic regulation across vertebrate species.