This paper responds to current concerns about quantitative methods for studying decision-making by describing the development of and results from an innovative transdisciplinary and mixed-methods tool for researching intrahousehold decision-making. The tool focuses specifically on decision-making about agricultural- and expenditure-related matters by spouses in marital or cohabiting relationships, although it could easily be adapted to alternative household compositions (e.g., mother–daughter dyads). The tool explores how decisions are made and why they are made alone or jointly.