This paper investigates the impact of the voluntary assurance of corporate social responsibility (CSR) reports on firms' operating performance. Using data from listed firms in Taiwan to test three theory‐driven hypotheses, we found that the voluntary assurance of CSR reports may not lead to firms' positive performance. However, both voluntary dual‐assurance and high confidence levels of assurance for CSR reports can positively influence such performance. We offer incremental insights into expanding the CSR literature by elaborating the importance of voluntary assurance. We suggest that firms voluntarily assure their CSR reports with a higher confidence level to further improve their performance.