This study investigates the role of IL-1 signaling in the differentiation and function of Th17 cells. IL-1R1 expression in T cells, induced by IL-6, is crucial for Th17-mediated autoimmunity and early Th17 differentiation in both in vitro and in vivo models. IL-1 signaling in T cells is essential for dendritic cell-mediated Th17 differentiation from naïve or regulatory precursors and synergizes with IL-6 and IL-23 to regulate Th17 differentiation and cytokine expression. IL-1 regulates the expression of IRF4 and RORγt during Th17 differentiation, and overexpression of these factors can lead to IL-1-independent Th17 polarization. These findings suggest that IL-1 plays a critical role in Th17 differentiation and may serve as a novel target for treating Th17-mediated immunopathology.This study investigates the role of IL-1 signaling in the differentiation and function of Th17 cells. IL-1R1 expression in T cells, induced by IL-6, is crucial for Th17-mediated autoimmunity and early Th17 differentiation in both in vitro and in vivo models. IL-1 signaling in T cells is essential for dendritic cell-mediated Th17 differentiation from naïve or regulatory precursors and synergizes with IL-6 and IL-23 to regulate Th17 differentiation and cytokine expression. IL-1 regulates the expression of IRF4 and RORγt during Th17 differentiation, and overexpression of these factors can lead to IL-1-independent Th17 polarization. These findings suggest that IL-1 plays a critical role in Th17 differentiation and may serve as a novel target for treating Th17-mediated immunopathology.