The investigative interviewing of victims, witnesses and suspects is one of the most frequent and important tasks undertaken by those conducting law enforcement investigations. Over the past 20 years or so, there has been a substantial growth in the amount of research examining the practice. Nonetheless, little research has been conducted into those interviews where an interpreter is increasingly present. Using a self-administered questionnaire, the present study examined the beliefs of 66 investigators and 40 interpreters in the context of international criminal investigations, concerning certain key tasks in such interpreter-assisted interviews. It was regularly found that there was not always a consensus of opinion either within or between these two groups of professionals concerning whether (when participating in investigative interviews) (1) they prepared jointly with each other; (2) interpreters assisted (or otherwise) with rapport building; (3) interpreters could interpret accurately; and (4) interpreter interventions were disruptive or not. Given such divisions of opinion, our findings tend to suggest that there is a lack of clarity as to the role of interpreters and, indeed, only personalised views as to what is best practice. The implications of our findings are discussed, and recommendations are made to enable practice enhancement.