This article builds on the literature on property rights and associational life in Latin America during and after transitions to democracy by assessing participation in voluntary associations as a determinant of land title. It uses survey data collected from rural properties near Santarém, Pará, to describe who participates in voluntary associations and, more important, whether participation in specific groups is aligned with possessing secure title, an important scarce resource in the Brazilian Amazon. This quantitative analysis shows that owners who participate in one union with state-controlled, corporatist roots are more likely to possess secure title to their land than those who do not participate. This systematic variation is important in an era of soy expansion, with a shift from small-scale subsistence farming to large-scale mechanized agricultural and a subsequent increase in land value.