In the aftermath of corporate scandals and the global fnancial crisis, the role of external auditors and of the internal audit function (IAF) has been critically scrutinized, and consequently, became even more in the focus of attention of external and internal stakeholders such as investors, regulators or corporate boards. Companies are under constant pressure to improve the reliability and accountability of their fnancial information, in order to comply with regulations and to compete efectively for capital in the global business environment. Since there is a certain degree of overlap between the tasks of internal and external auditors, e.g. regarding an evaluation of the efectiveness of internal controls,1 there are many opportunities for coordination and cooperation between the two functions that may yield synergistic outcomes for both sides, such as higher quality audits and economic benefts. On the one hand, external auditors may utilize the experience of the internal auditors to reduce work duplication and, in efect, the cost of the external audit (Stein et  al. 1994; Felix et  al. 2001; Al-Twaijry et  al. 2004; Lin et al. 2011; Pizzini et al. 2015). In addition, internal auditors could help external auditors to understand the company’s internal control system and the level of compliance with it.2 Due to its unique position within a company as a supporting and assuring instrument of the board and the audit committee, the IAF will potentially collaborate with the external auditors, because such collaboration potentially increases the efectiveness as well as the efciency of the external audit and the realisation of such a potential is valuable for a company. On the other hand, internal auditors may beneft from the expertise of external auditors in areas where the internal audit department needs support (Haron et al. 2004; Schneider 2009). In certain situations, an assistance from the external auditors is preferable in comparison to outsourcing or co-sourcing arrangements, because of their particular knowledge and expertise and because additional cost might be avoided. Coordination and cooperation between internal and external auditors might enable the internal auditor to beneft from the external auditors’ exposure to a wider variety of fnancial issues and knowledge about similar businesses or organizations (Fowzia 2010; Endaya 2014). Moreover, it avoids that internal auditors duplicate external auditors’ work, which results in wasted internal audit time. The elimination of redundant work will possibly leave time and resources for better audit coverage (Morrill and Morrill 2003). In addition, the IAF could use the fndings of external auditors to assess risks and to determine areas that need their future attention (Saidin 2010). Mutual communication between internal and external auditors potentially provides the IAF further insights into audit techniques and methods.3 However, it is important to note that a useful cooperation between internal and external auditors does not only require similar audit objectives but also similar audit scopes.