Assuming that corporate social responsibility (CSR) is “a process of accumulating knowledge and experience” (Tang et al., 2012, p. 1298), this paper aims to investigate whether and how CSR knowledge (Asif et al., 2013; Kim, 2017) affects financial performance in the European banking industry. The empirical research analyses a panel of 72 banks from 20 European countries over seven years (2009-2015). The hypotheses were tested using fixed effects regression analysis and the two-stage Heckman model (1976) to address endogeneity bias. The findings of this work are twofold. First, consistent with the concept of knowledge absorptive capacity (Cohen and Levinthal, 1990), the internal CSR of banks (Kim et al., 2010) positively affects citizenship performance (Peterson, 2004a). Second, in line with the reputational effect of CSR (Margolis et al., 2009; Bushman and Wittenberg-Moerman, 2012), citizenship performance is a positive predictor of a bank’s financial performance. From a knowledge-based perspective, the analysis shows that accrued internal CSR knowledge plays a key role in implementing effective CSR programs for external stakeholders. Moreover, this study shows how CSR engagement in external initiatives can improve a bank’s competitiveness because of the relationship between citizenship performance and the positive reputation of a bank. The management of CSR initiatives may favor the sharing of knowledge and creation of trust relationships among banks and internal and external stakeholders. CSR knowledge contributes to expanded value creation for both society and banks. The knowledge management perspective of CSR provides new insights into the sustainability of banks’ business models and contributes to advancing the debate on the governance modes and effects of CSR. Moreover, the CSR perspective offers additional opportunities for addressing the challenges associated with sharing tacit knowledge within and outside of organizations.