This study aims to analyze methods for assessing the socioeconomic impact of COP30 in Belém/PA for the municipality s inhabitants, considering the legacies of large-scale mega-events. The research is based on the assumption that events such as the Conference of the Parties generate significant transformations in host cities, encompassing economic, urban, and social aspects. The work adopts a qualitative approach. The different methods used indicate various ways to improve the population s quality of life, although some challenges such as social inequality persist. It is concluded that COP30 represents a unique opportunity to leverage sustainable development in Belém, provided it is accompanied by effective public policies and continuous monitoring. The adoption of an integrated system of indicators is recommended to ensure the event s legacies are inclusive and longlasting.