ABSTRACT Recent research finds that investors' assessments of a stock's fundamental value are influenced by corporate social responsibility (CSR) performance through the affect‐as‐information heuristic. We extend prior research by examining two boundary conditions for the use of this heuristic: (i) whether the CSR performance relates to activities that are integrated in a firm's core business practices (material CSR issues) or not (immaterial CSR issues), and (ii) whether the CSR performance is positive or negative. Employing an experimental method, we find that the affect‐as‐information heuristic applies only to immaterial CSR issues but not to material CSR issues, and only to positive but not negative CSR performance. Our findings suggest that investors likely use a heuristic approach to process immaterial and positive CSR issues, and a more deliberate and systematic approach to process material or negative CSR issues. Our study has both practical and theoretical implications.