The aim of this study is to analyze how environmental and social sustainability asymmetries in buyer-supplier relationships affect the buyer financial and market performance. In particular, we draw from legitimacy theory to explain how sustainability asymmetries affect firm performance. The hypotheses are tested using a longitudinal dataset of 516 buyer firms belonging to sensitive industries and their top suppliers. Results suggest that, contrary to earlier studies, sustainability asymmetries may have a positive effect on financial performance. Moreover, we detected that whereas environmental asymmetries have a significant impact on firm performance, social asymmetries do not. In addition, results suggest that, within the environmental dimension, asymmetries have different effects, depending on the environmental sub-dimension. For example, while having a higher buyer-supplier asymmetry in the resource reduction area improves buyer profitability, in the area of emissions it leads to a negative performance. Also, research shows that such impact will depend on which party is leading the sustainability initiatives (i.e. buyer or supplier). The main managerial implication is that investing in reducing buyer-supplier sustainability asymmetries can be counterproductive in certain dimensions, whereas in other ones it could actually improve financial and market performance.