This article investigates the credit card debt puzzle. Simultaneously holding credit card debt and liquid assets is puzzling given the sizeable difference between interest rates of debt and assets. However, this behavior is common—about 31% of households in the 2016 Survey of Consumer Finances. The cost of co-holding may be justified if consumers anticipate future restrictions in credit or if they need to maintain liquidity. Other existing explanations for co-holding include impulsive spending and low financial literacy. This research reveals a new explanation for the credit card debt puzzle: consumers’ overconfidence of their financial knowledge. Using a Coarsened Exact Matching method, we found that overconfident consumers were 20%–40% more likely to co-hold credit card debt and liquid assets.