Some recommendations made by the World Parks Congress in Durban (2003) underscore the need to consider the impacts of multi-purpose marine protected areas (MPAs) on resident or adjacent populations, and lead social and fisheries scientists to reconsider their approaches and methods regarding the assessment of economic effects of an MPA. This paper contributes to this reconsideration by proposing an assessment method of microeconomic effects. The approach is the comparison of fishing households’ economic situation in Chumphon Province (Thailand) at a given time based on their location in relation to a marine protected area: within or adjacent to Chumphon Archipelago Marine National Park vs. remote from it. We address three economic dimensions: the profitability of household activities, the income-distributional effects among households and the household vulnerability. This assessment requires the calculation of five indicators : the net income, the net profit margin, the Gini coefficient and the Herfindahl index, and Bene's vulnerability index. From a dataset made up of 123 fishing households surveyed twice a year, the main results show higher incomes and less economic vulnerability for households located within or adjacent to the MPA, and a more inegalitarian income distribution among households located remote from the MPA. So, the households located within or adjacent to the MPA have more security, can stay focused on the most profitable fishing activities and not have to diversify outside of the fishing sector. In an environment where commercial small-scale fishing was already highly developed, setting up an MPA could have the effect of sustaining an efficient, specialised professional set-up for fishing households in the area concerned. With respect to a policy to establish MPAs in keeping with the Durban recommendations, this study shows that a thorough analysis of profitability, income distribution and economic vulnerability should help to identify who the winners and losers might be, which could improve the targeting of mitigation and compensation measures.