We study the effects of adult financial education using a large-scale randomized controlled trial linked to administrative credit register data. The intervention consists of a structured ten-hour personal finance course involving more than 10,000 people in Portugal. Six months after the program, treated individuals exhibit significant improvements in financial knowledge, especially among women, low-income and low-education individuals, and participants with low baseline financial literacy. The intervention also improves self-reported confidence, financial attitudes, and behaviors, including budgeting, saving, retirement planning, informed use of financial products, and financial market participation. Using loan-level administrative data, we find significant changes in debt management: treated individuals reduce reliance on high-cost credit card balances while preserving credit access, experience fewer delinquencies, and are more likely to renegotiate mortgages. Our results suggest that financial education can reduce financial literacy gaps and improve household balance sheet management, even within relatively affluent populations in high-income countries.