Authoritative standards encourage external auditors to coordinate their efforts with the client’s internal audit function (IAF) as part of a financial statement audit. Academic research on this relationship finds that it has the potential to improve audit quality and efficiency. The objective of this research is to better understand how coordination can impact the external auditor’s decision to rely on the IAF. Prior research has shown that the reliance decision is complex and involves several factors that must be considered simultaneously. In this study, we surveyed external auditors to better understand the benefits of coordinating efforts, the antecedents to successful coordination, and the elements that potentially inhibit external auditors from relying on the work of internal auditors. We find that external auditors are coordinating with the IAF to achieve more efficient and effective audits. The degree of this reliance, however, does vary between audits and is largely dependent upon the perceived competence and objectivity of the IAF as well as effective communication. Our findings are informative to external audit practitioners and their decision to rely on IAFs and work towards a successful arrangement where the integrated audit is applied more efficiently and effectively. This additional insight also helps inform and direct future research into external auditors’ coordination decisions.