Purpose – Drawing on legitimacy theory, this study aims to investigate whether the benefits of the external assurance process pass beyond the current period and help firms improve corporate social responsibility (CSR) performance in the subsequent periods. Furthermore, the authors examine whether corporate governance (CG) and firm visibility moderate the relationship between assurance and CSR performance. Design/methodology/approach – The authors retrieved data from Thomson Reuters from 2002 to 2019 and executed a fixed-effects (FE) panel regression analysis. The country-level sample distribution includes 63 countries with 4,625 unique firms and 29,054 data points within these countries. The authors run several robustness tests using an alternative subsample, instrumental variable regression analysis, country-industry-year FE regression analysis, excluding the financial sector and including additional control variables and regression analysis based on propensity score matching. Findings – The findings indicate that external assurance helps firms achieve greater CSR performance in the current period and the subsequent two periods following external assurance. However, external assurance exerts its strongest positive impact on CSR performance in the current period, and its influence extends, albeit at a weaker level, to the following two periods. Furthermore, the first moderation analysis reveals that governance structure helps firms translate the assurance process into the greater social performance but does not help to achieve higher environmental performance. The second moderation analysis reveals that firm visibility/size positively moderates between the assurance process and governance and social performance but not between the assurance process and environmental performance. Originality/value – Despite the concurrent association between CSR performance and assurance being examined before, the lag-lead relationship is the novelty of the study to highlight the long-term effect of assurance on CSR performance. Besides, although the direct effect of both CG practices and firm visibility on CSR performance and the external assurance process has been investigated before, the authors extend the literature by examining the moderating effect of CG practices and firm visibility on the external assurance and CSR performance relationship. This provides a better explanation of the extent to which the effect of external assurance on CSR performance is constructed and conditioned by CG practices and firm visibility, thereby drawing attention to contingencies’ role in firms’ practices.