The Millennial generation’s financial behaviors are of great importance because they will contribute significantly to the labor market in the future. Using the 2015 National Financial Capability Study (NFCS) dataset, we examine the relationships between Millennials’ propensity to plan, financial knowledge, and credit card management behaviors. The findings reveal that a propensity to plan was positively associated with appropriate credit card management behaviors but it was negatively associated with irresponsible behaviors. A similar relationship was found between objective financial knowledge credit card management behaviors, while subjective financial knowledge was positively related to inappropriate management behaviors instead. Millennials who are overconfident about their financial knowledge are more likely to engage in costly management behaviors. This was a robust result found across various overconfidence measures.