Interest in household food insecurity (FI) within scientific and policy groups has motivated efforts to develop methods for measuring it. Questionnaires asking about FI experiences have been shown to be valid in the contexts in which they were created. The issue has arisen as to whether such questionnaires need be developed from the ground up or if a generic questionnaire can be adapted to a particular context. This study aimed to gain an in-depth understanding of household FI in urban Costa Rica, develop and validate a questionnaire for its measurement, and inform the choice between the 2 methods of development. The study was conducting using qualitative and quantitative methods provided in the Food and Nutrition Technical Assistance (FANTA) guidelines. In-depth interviews were conducted with 49 low-middle-income urban women using a semistructured interview guide. A 14-item FI questionnaire was developed based on results from these interviews. A field study was conducted in 213 households. The results show that the developed questionnaire provides valid measurement of household FI in urban Costa Rica and is simple and quick to apply in the household setting. FANTA developed a guide during the period that this research was completed that provides a generic questionnaire that can be adapted for use in various countries, rather than building the questionnaire from the ground up. This study provides evidence that careful attention to the procedures in this guide will likely yield a questionnaire suitable for assessing household FI in middle-income countries.