<p>Precise regulation of the immune system is essential for maintaining physiological homeostasis and treating disease. Insufficient immune activation would lead to tumor development, whereas excessive immune responses could cause autoimmune diseases or chronic inflammation. Due to the advantage on the composition, morphology, catalytic functions, degradability, and inherent bioactivity, inorganic biomaterials have transformed from conventional carriers into versatile platforms capable of actively regulating immune responses. Recent progress in the development of immunoregulatory inorganic biomaterials, highlighting their dual capacities to induce immune activation or immune suppression, was summarized in this review. For immune activation, inorganic materials could serve as adjuvants to enhance antigen presentation, induce immunogenic cell death (ICD), and reprogram immune cell metabolism, thereby enabling applications in tumor treatment. For immune suppression, specific inorganic materials can effectively eliminate excessive reactive oxygen species (ROS), modulate the functions of inflammatory cells such as neutrophils and promote the development of immunosuppressive cell populations, including regulatory T cells and M2 macrophages, thereby reestablishing the immune tolerance in autoimmune diseases. Despite the remaining challenges in function mechanistic verification, long-term biosafety, and clinical translation, inorganic biomaterials offer a promising strategy and multifunctional platform for achieving precise immune interventions across cancer immunotherapy, tissue regeneration, and autoimmune disease management.</p>