The paper investigates the effect of co-operative membership on people’s capability to participate in household decision-making and on domestic gender relations. Our hypothesis is that the democratisation process activated in genuine co-operatives, authentic member-owned forms of business, may then be transferred to the household. We tested this in the “Coppalj” co-operative in Brazil, where we collected primary data. Both the techniques employed, regression and propensity score matching, support our hypotheses in a number of life domains. Though results vary slightly according to the domain and the outcome indicator, they show that members of the co-operative have a statistically significant higher capability to participate in decision-making and to share their decisions with partners than non-members (the control group). We then triangulated these quantitative outcomes with qualitative ones: the latter confirm an improvement in gender relations between co-operators and their partners, highlighting the fundamental role of Coppalj in fostering gender equality.