The purpose of this study is to explore how external auditors experience their decision to rely on internal auditors’ work. This study employs both qualitative and quantitative methods consisting of semi-structured interviews and questionnaires administered to external auditors in Sweden. Semi-structured interviews were conducted with external auditors who are working in Big 4 audit firms in Sweden and have engagements with internal audit functions. A questionnaire was administered to authorized/approved auditors, members of the Swedish Association of Certified Public Accountants (FAR). Findings indicate that external auditors use the work of internal auditors as they gain efficiency in performing their work. Nevertheless, external auditors may compromise their independence and professionalism through closer involvement with internal auditors, which may lead to uncritical evaluation and use of the reports prepared by internal auditors. At the same time, while relying on the internal auditors’ reports, external auditors appear to be conscious of the consequences for the audit quality they deliver. The study highlights the dilemma faced by external auditors in their cooperative work with internal auditors and the balance/imbalance in their opinions concerning efficiency gains, independence, professionalism and audit quality.