In response to investors and other stakeholders questioning the credibility of the performance information displayed in sustainability reports, companies increasingly have their sustainability reports voluntarily assured by an independent third party. However, voluntary third‐party assurance on sustainability reports (SA) may vary considerably in terms of the choice of the assurance provider as well as the scope and level of assurance. In this study, the relationship between corporate sustainability performance (CSP) and choices related to SA is explored. Using a panel data set of 4686 listed companies (from 21 European and North American countries) during the period 2009–2014, the results indicate that companies with a superior CSP are more likely to employ third parties to provide assurance on their sustainability reports than companies with an inferior sustainability performance. For companies that employ third parties to provide assurance, we also find that, among the companies headquartered in the more shareholder‐oriented countries, CSP plays a significant role in explaining variation in the choice of the assurance provider, while predominantly in the more stakeholder‐oriented countries, companies with a good CSP are more likely to choose a broader assurance scope than companies with a poor CSP. The results support the notion that companies with a superior CSP make different choices related to SA than companies with an inferior CSP. The results also indicate that country‐specific characteristics are important for understanding the variation in choices related to SA. We discuss the findings and their implications. © 2017 The Authors. Corporate Social Responsibility and Environmental Management published by ERP Environment and John Wiley & Sons Ltd.