Background <p>Infectious bronchitis virus (IBV) is a highly contagious virus in poultry causing significant economic losses. Despite the implementation of various vaccines, the continuous emergence of regional variants had made complete protection challenging. T cell responses are critical for immunity against viral infections; however, a deeper understanding in avian T cell-mediated immune responses to IBV is still needed.</p> Results <p>In this study, we isolated splenocytes form 4–to 8-week-old specific-pathogen free (SPF) chickens and investigated their immune responses to the IBV strain K047-12. The IBV infection induced CD25^high T cells during in vitro splenocyte culture and elevated gene expression of <i>IL10</i> and <i>IL12B</i>, indicating T cell activation and a regulatory immune reaction. To further characterize CD8⁺ T cell–specific responses, we sorted CD44⁺ CD8⁺ T cells following IBV infection and performed transcriptomic analysis using two independent biological replicates per group. As result, IBV infection modulated multiple immune-related pathways, including the cytokine–cytokine interaction and TGF-β signaling pathways. Moreover, infected CD8⁺ T cells exhibited upregulation of <i>IL6R</i>,<i> IL7R</i> and <i>NFKB1</i> genes associated with memory precursor and activated T cell status (CD44⁺), suggesting a potential shift toward a memory-like state.</p> Conclusions <p>These findings suggest that IBV infection promotes activation and differentiation of CD8⁺ T cells, potentially driving a shift toward a memory-like phenotype. This information could enhance the understanding of avian antiviral T cell immunity and support the development of T cell–based protective strategy targeting IBV variants.</p>