CO₂ geological storage is a pivotal technology for achieving the global targets of carbon peaking and carbon neutrality. However, the potential risks of CO₂ leakage to environmental safety and long-term storage efficacy are significant, thereby making the establishment of robust and reliable monitoring systems indispensable. This review systematically explores the potential leakage pathways and key monitoring parameters, including wellbore integrity, CO₂ plume migration, and caprock stability. In addition, the mechanisms and influencing factors associated with the three primary CO₂ leakage pathways are systematically summarized. This approach provides a critical assessment of the advantages, applicability and limitations of prevalent geophysical and geochemical monitoring methods. A special focus is placed on optical fiber sensing technology, whose research progress and application feasibility in laboratory settings are summarized in terms of monitoring targets, measurement accuracy and sensing range. Furthermore, this review highlights several global carbon capture and storage demonstration projects to illustrate the integration and performance of various monitoring technologies in practical engineering. To ensure the efficiency and safety of CO₂ geological storage in the future, it is necessary to develop advanced monitoring technologies, such as optical fiber sensing and promoting the integrated deployment of multi-modal monitoring systems. These efforts are considered essential for supporting the large-scale deployment of carbon capture, utilization and storage engineering, particularly in the context of China.