Recently, internal audit functions (IAFs) have gained increasing prevalence and enhanced status in companies. Such developments have been prompted by worldwide regulatory pressure for improved corporate governance owing to major financial scandals in the early 2000s. In the US, the New York Stock Exchange (NYSE) has mandated that listed companies formalise their IAFs since 2004, and the NASDAQ has considered adopting a similar rule (Securities and Exchange Commission (SEC) 2013). Outside the US, IAFs remain largely voluntary, but they are recommended as a ‘best practice’ for corporate governance in numerous countries (e.g. the UK, Denmark, Switzerland, and Sweden) and have become a common feature of medium to large companies worldwide (Mennicken and Power 2013). Evidence from prior studies shows that a high-quality IAF may have various benefits for firms, for instance, by improving internal controls, constraining earnings manipulation and fraud, reducing audit costs, and enhancing audit efficiency (Felix et al. 2001, Prawitt et al. 2009, Lin et al. 2011, Messier et al. 2011, Ege 2015, Pizzini et al. 2015). Because of the increasing prevalence and importance of IAFs and increasing regulatory attention on IAFs to enhance the quality of corporate governance worldwide (National Association of Corporate Directors (NACD) 1999, SEC 2002, Gramling et al. 2004, SEC 2004, Glover et al. 2008), there is a growing need to understand IAF quality in the current corporate governance context (Sarens 2009). Do variations occur in IAF quality? What are the internal and external factors that incentivise firms to establish high-quality IAFs? Given the complexity of corporate governance structures, what are the relationships between IAFs and other parties in the corporate governance mosaic? These questions are the impetus of our study. We extend prior research by exploring organisational and environmental factors that are associated with high-quality IAFs in an international context. Despite the significant increase in the number of studies on IAFs, most studies have been limited to single-country settings. An international setting offers more diverse levels of internal organisational structures, additional levels of operational complexity, and various external environmental conditions. A better understanding of the factors that influence firms’ incentives to develop high-quality IAFs in an international setting not only adds to our knowledge of IAFs but also facilitates awareness of governance practices worldwide