Centered on the U.S. market, numerous studies have been conducted since the early 1990s to identify the causes of high interest rates in the credit card market. The causes suggested in prior research include adverse selection problems in the credit card market, moral hazard of cardholders, switching costs, search costs, transaction costs, and other factors such as cardholder irrationality. Using micro-level data from domestic specialized credit card companies, this study primarily examines whether downward interest rate rigidity exists in the Korean credit card market and analyzes whether the verifiable problems of adverse selection and moral hazard are present. The main findings of this study are as follows. In the Korean credit card market, downward interest rate rigidity was found to exist, as the magnitude of interest rate increases when funding rates rose was greater than the magnitude of interest rate decreases when funding rates fell. Regarding adverse selection, when credit limits were increased, the credit utilization rate for the high-credit group remained unchanged, while the outstanding balance for the low-credit group increased significantly, suggesting the possible existence of adverse selection. However, with respect to interest rates, adverse selection problems were not found under either declining or rising interest rate conditions. Finally, although the utilization rate increased as the delinquency month approached, this was attributable to decreases in credit limits, and the hypothesis that cardholders would exercise the option value at the point when the probability of default is maximized was not supported.