This study attempts to reveal the negative effects of customer complaints on a firm’s financial performance and, by using empirical analysis, to find out whether a firm’s Corporate Social Responsibility (CSR) activities can reduce the negative impacts of those complaints. For this purpose, we collected panel data on 49 companies in the financial industries. Records of consumers' complaints to financial firms were used as a measure for customer complaints, and the amount of donations in the firm’s individual profit and loss statement was used as a measure for the firm’s CSR activities. For the firm’s performance, we used the Return on Assets (ROA). Using these panel data, we conducted a dynamic panel model analysis to reflect the unique characteristics of the firm in the model. We found that customer complaints do act negatively on a firm’s performance, but we also confirmed that a firm with bigger invests in CSR activities, the less adversely customer complaints affect the firm’s performance.