Using comprehensive data on U.S. corporate bond trades since 2002, we find that retail bond investors over-rely on untimely credit ratings, neglect firm fundamentals, and appear to misunderstand the trade-off between bond risk and yields. Specifically, retail investors appear to select bonds by first screening on a credit rating level and then sorting by yield, buying the highest-yielding bonds within each rating level. Because yields lead credit ratings, selecting on yield-within-rating means that retail investors systematically trade in the opposite direction of accounting fundamentals, buy in advance of credit downgrades and defaults, and generate negative average future returns. Overall, our findings indicate that retail bond investors systematically mislearn from prices, which is hard to reconcile with standard notions of rationality. Our study provides new evidence of ill-informed trading in a market that is thought to be relatively sophisticated, and contributes to our understanding of the roles and consequences of credit ratings in debt markets.