Costly signaling theory suggests that individuals might be more likely to consume sustainable food products if doing so signals an underlying prosocial value to others. However, it is unclear whether prosocial signals are equally interpreted by others. We study whether consumers of carbon-labeled (vs. non carbon-labeled) products are perceived more positively and if observers’ biospheric values and product prices influence such perceptions. An experimental study (N = 229) assessed participants’ perceptions of consumers of carbon and non-carbon labeled food products described as being either cheaper or more-expensive-than-average. Results indicated that consumers of carbon-labeled products were perceived more positively and that such perceptions were accentuated when observers strongly endorsed biospheric values. Further, positive perceptions of consumers occurred regardless of a product’s price, although effects were strongest amongst observers with high biospheric value endorsement when products were cheap and carbon-labeled. Implications for carbon labeling initiatives and food marketing more generally are discussed.