Protected areas (PAs) are pivotal for biodiversity conservation, particularly in developing countries. However, success in achieving their objectives is variable. The reasons for the inconsistent effectiveness of PAs are well documented and include inadequate resources and conflicting objectives. Despite the proliferation of tools and guidelines for monitoring and evaluation (M&E) of PAs over recent decades, a gap persists between the availability of these resources and their practical application. This review of more than 114 publications on the subject summarizes and critically examines the approaches and tools used for M&E of PAs, in particular in developing countries. It highlights the existing shortcomings and explores the causes behind the ongoing disconnect between theoretical guidance and operational reality. Based on this review, we suggest recommendations to improve the efficacy and sustainability of M&E practices in the PAs of developing countries, with an emphasis on integrating the needs of local communities and adopting a strategy of adaptive management.