Enhancing the sustainability of the agri-food supply chain is dependent on the active and informed participation of consumers. Food product certifications can aid consumers in making better-informed purchasing decisions. This research examines consumers’ perceptions of the sustainability features of two institutional short-chain certifications, which indicate the local and short supply chain origins of products. The data were obtained from a sample of 295 Catalan consumers stratified by gender, age, and income level. The respondents were surveyed face to face in an experimental environment and asked to rate 20 sustainability indicators on a seven-point Likert scale based on the Food and Agriculture Organization (FAO)’s Sustainability Assessment of Food and Agriculture systems (SAFA), with fig jam as the case study. The results showed that consumers believe that purchasing certified fig jam contributes to improving agri-food supply chain sustainability, particularly concerning farmers’ economic (local procurement) and governance (transparency) indicators. The heterogeneity analysis revealed a correlation between trust in the certification, purchase intention toward certified fig jams, and higher sustainability perceptions, particularly among the enthusiastic cluster of consumers. However, prior knowledge of the certification was not a significant factor. The findings indicate that the promotion of direct sales and short-chain certifications by institutional authorities and businesses may encourage consumers to make sustainable purchasing decisions. To facilitate informed purchasing, policymakers must advance toward the clear and reliable certification of the contribution that agri-food products make to sustainability in all its dimensions.