Small Island Developing States (SIDS) are disproportionately affected by climate change, with impacts threatening their communities, ecosystems, and economies. Nature-based solutions (NbS) offer a promising approach to address these challenges, yet their effectiveness in SIDS remains poorly understood. Researchers systematically reviewed 49 studies reporting 53 NbS interventions across 26 SIDS and found that nearly three-quarters of cases reported positive climate outcomes, though only half provided clear evidence, and fewer employed baselines, counterfactuals, or thresholds. Evidence was skewed toward croplands and agroforestry, while coastal ecosystems were underrepresented.