<p>Despite current medicine’s fast-paced advances, many acute and chronic illnesses still lack truly effective and safe therapies. Cancer treatments often lead to off-target healthy tissue damage and poor therapeutic outcomes, wound standard treatments generally demonstrate poor healing efficacy and increased susceptibility to infection, and bone tissue engineering and myocardial tissue engineering can result in immunological rejection and limited availability. To tackle these issues, injectable hydrogels have emerged, and through the incorporation of nanoparticles, nanocomposite hydrogels have appeared as versatile platforms, offering improved biocompatibility, mechanical strength, stability, and precise controlled drug release, as well as targeted delivery with increased drug retention at the site of action, reducing systemic drug distribution to non-target sites. With the ability to deliver a diverse range of therapeutic entities, including low molecular weight drugs, proteins, antibodies, and even isolated cells, injectable nanocomposite hydrogels have revolutionized current therapies, working as multifunctional platforms capable of improving efficacy and safety in cancer treatment, including in chemotherapy, immunotherapy, photothermal therapy, magnetic hyperthermia, photodynamic therapy, chemodynamic therapy, radiotherapy, molecularly targeted therapy, and after tumor surgical removal, and in general, chronic diabetic or tumor-induced wound healing, as well as in bone tissue engineering and myocardial tissue engineering. This review provides a thorough summary and critical insight of current advances on injectable nanocomposite hydrogels as an innovative approach that could bring substantial contributions to biomedical research and clinical practice, with a focus on their applications in cancer therapy, wound healing management, and tissue engineering.</p> Graphical Abstract <p></p>