Integrated reporting is a key instrument used to inform stakeholders about the sustainability issues of a company. Only an assured report can effectively instill confidence in its users regarding the sustainability of the company. Based on the International Integrated Reporting Framework issued by the International Integrated Reporting Council (IIRC), the authors solicited perceptions from auditors and audit report users about several aspects of integrated reporting assurance. An analysis of the responses suggests that integrated reporting assurance is important, but there are many challenges (both methodological and related to the characteristics of non-financial information) for auditors to overcome. Reporting companies and auditors must work to overcome these problems. The former ones must improve the quality of non-financial information and the later must adapt their audit procedures. This paper provides valuable insights into preferences regarding the form and content of the audit report on integrated reporting. This study is useful to regulators of audit activity, auditors’ corporations, the IIRC, and other international associations, academics, and audit report users, and contributes to the current integrated reporting literature by examining the perceptions of auditors and users regarding the assurance of integrated reporting. Integrated reporting assurance is still an under-explored field of research.