Assessing the impact of CSR initiatives can be a complex task for marketers given the variety of methods of communicating about CSR as well as the broad range of stakeholders that CSR initiatives might interest. Social media helps increase the visibility and credibility of CSR communication and provides new ways of reaching and involving stakeholders in CSR initiatives. Using data collected and coded from Facebook pages of the Top 100 Global Brands, the authors introduce a new measure of effectiveness for CSR communication; CSR communication productivity (CCP). The findings indicate that CCP has a positive impact on firm performance (Tobin’s Q). The authors also investigate the impact of External Stakeholder Involvement in CSR initiatives. The results suggest that when external stakeholders are involved in an organization’s CSR initiatives, both CCP and firm performance (Tobin’s Q) improve. In addition, third-party evaluations of CSR performance positively moderate the impact of External Stakeholder Involvement on CCP. These findings offer contributions to CSR communication and social media marketing theories. They also have implications for marketing managers regarding how to measure and benchmark CCP, and how to maximize returns by involving external stakeholders in CSR efforts.