<p>CaCO₃ is a well-known mineral that has been used extensively as an additive to improve the processability and as a reinforcement material for industrial-based applications. Recently, emphasis has been laid on the fabrication of CaCO₃-based nanoplatforms for enhanced drug and vectors for gene delivery, biosensing, and bioimaging, combinatorial effects of photothermal and photodynamic therapies to treat tumors and cancers. For instance, Fe₃O₄@CaCO₃ nanocomposites not only exhibit excellent biocompatibility in cancer chemotherapy but also provide magnetic separability for reuse in pollutant remediation. Similarly, the association of C dots with CaCO₃ has huge potential in the fabrication of novel and advanced biomaterials that can serve as platforms for various biological and biotechnological-based applications. On the environmental aspect, CaCO₃ nanohybrids have shown efficacy in adsorbing heavy metals, degrading dyes, and even acting as slow-release fertilizers, aligning with sustainable agriculture and circular economy models. Thus, there is a lot of scope for the fabrication of novel CaCO₃-based nanohybrids in the future, and this review highlights the recent advances and developments in this direction. Despite these advances, key gaps and challenges still remain that need to be addressed. Current studies are mostly confined to laboratory settings, with limited translation into clinical or field-scale applications. The challenges include optimizing particle size, morphology, and stability under physiological and environmental conditions, with more emphasis on issues pertaining to biosafety and long-term ecological impacts. Future research must focus on interdisciplinary strategies integrating green synthesis, advanced functionalization, and rigorous in vivo/field trials to fully harness CaCO₃ nanohybrids as multifunctional platforms that aid in biomedical innovation with environmental sustainability.</p> Graphical abstract <p></p>