•There is a need to put local people at the center of evaluations exploring the impacts of conservation on human well-being.•The Global Person Generated Index (GPGI) allows people to define their own well-being.•Participatory impact evaluation explores local people’s perception of the impact of conservation on their well-being.•By learning from such approaches, conservationists can improve interventions and gain much needed local support. There is growing interest in the importance of ensuring that biodiversity conservation is not achieved at the expense of local people’s well-being. It has been suggested that when evaluating the impact of an intervention, the affected population should be allowed to define well-being (requiring a subjective measure), and impacts (requiring a participatory approach), but very few, if any, conservation evaluations live up to these standards. We used a participatory impact evaluation approach with the Global Person Generated Index (GPGI) to investigate the relative impacts of strict protection and community forest management on local well-being in Madagascar’s rainforests. The GPGI captures the subjective and multidimensional nature of well-being by asking respondents to identify the five most important domains for their quality of life, to evaluate their own performance in each domain, and the relative importance of the five identified domains. Participatory impact evaluation establishes local perceptions of the cause-effect relationship between an intervention and respondents’ performance in each domain. Over half the respondents perceived no positive or negative impacts from the conservation interventions. We found no significant difference between strict protection and community forest management in the measures we used to examine the magnitude of their relative impacts, but there were differences in the characteristics of domains impacted and in the priority domains that could be targeted to improve well-being in locally meaningful ways. Because of its subjectivity, the GPGI cannot provide quantitative information on the magnitude of impacts. Its strength lies in the wealth of information it provides on what life domains people value and their performance in these domains. Combined with the participatory impact evaluation approach, the GPGI provides highly relevant insights that can be used to improve interventions in ways which increase the local legitimacy and acceptability of conservation initiatives.