Interleukin (IL)‐33, a member of the IL‐1 superfamily, functions as an alarm signal, which is released upon cell injury or tissue damage to alert the immune system. It has emerged as a chief orchestrator in immunity and has a broad pleiotropic action that influences differentiation, maintenance and function of various immune cell types via the ST2 receptor. Although it has been strongly associated with immunopathology, critically, IL‐33 is involved in host defence, tissue repair and homeostasis. In this review, we provide an overview of the signalling pathway of IL‐33 and highlight its regulatory functions in immune cells. Furthermore, we attempt a broader discussion of the emerging functions of IL‐33 in host defence, tissue repair, metabolism, inflammatory disease and cancer, suggesting potential avenues to manoeuvre IL‐33/ST2 signalling as treatment options.