Purpose This study aims to examine the nature and extent of internal auditors’ (IAs) involvement in corporate social responsibility (CSR) assurance. It also ascertains the capacity building requirements to legitimise the role of IAs as a credible form of providing CSR assurance. Design/methodology/approach A qualitative research approach was adopted, where data were collected through semi-structured interview of IAs of companies in Ghana that produce CSR reports. Findings Findings suggest that companies appreciate the fact that the internal audit function could provide independent assurance on CSR reports. However, there is limited information on the nature and scope of the assurance procedures. Moreover, most IAs seem to lack the requisite knowledge and skills needed to effectively carry out CSR assurance engagements. These evidences suggest a relatively low level of reliance being placed on CSR assurance services provided internally. Research limitations/implications Findings are purely based on the perceptions of IAs. Future studies may include the views of those who appoint IAs (i.e. management). Practical implications Findings engender discussions on the need for IAs and regulators of IAs (e.g. the Institute of Internal Auditors), particularly those in developing countries to begin to conscientise practitioners on the changing roles of the IA in the areas of CSR and CSR assurance. Originality/value This study is one of the very few studies on CSR assurance from the perspective of IAs and it also based on evidence from an African context. Also, the study provides evidence on the need for a deliberate effort to equip internal audit practitioners to provide at least some minimal assurance on CSR disclosures and reports.