This study empirically examines the relationship between a firm’s fulfilling of corporate social responsibility (CSR) and performance. We developed a CSR index (CSRI) to quantitatively evaluate CSR, which consists of four dimensions measuring a firm’s contributions to the economy, society, environment, and corporate governance, respectively. With data from publicly-listed firms in Taiwan during the period of 2004–2009, results of quantile regression show that fulfilling CSR has a significantly positive impact on firm performance, and that the impact in a more profitable firm tends to be significantly greater than that in a less profitable firm. Specifically, when a firm is more profitable, its management would be more willing to implement CSR. The implication is that a firm could pursue better performance while serving as a good corporate citizen.