Agricultural sustainability is actually measured based on indicators. The choice of indicators is made by scientists alone and is rarely explained. Therefore, the sustainability assessment may be biased because it does not take into account the field knowledge of farmers and agricultural extension officers. Here, we used a novel method using participatory indicators in four steps: (1) group discussions with stakeholders, (2) a survey questionnaire, (3) a household survey, and (4) an estimation of sustainability level. We applied this method to Benin, West Africa, and defined 17 indicators. Some indicators were similar to known indicators, whereas other indicators measured the environmental and social dimensions of sustainability. The method was applied to a case study of maize farming. We found values of 41 for economic sustainability, 55 for environmental sustainability, and 40 for social sustainability. This finding evidences some weaknesses of maize farming in northern Benin because the sustainability threshold value is 50.