Background: There is a need for clinical tools to identify cultural issues in diagnostic assessment. Aims: To assess the feasibility, acceptability and clinical utility of the DSM-5 Cultural Formulation Interview (CFI) in routine clinical practice. Method: Mixed-methods evaluation of field trial data from six countries. The CFI was administered to diagnostically diverse psychiatric out-patients during a diagnostic interview. In post-evaluation sessions, patients and clinicians completed debriefing qualitative interviews and Likert-scale questionnaires. The duration of CFI administration and the full diagnostic session were monitored. Results: Mixed-methods data from 318 patients and 75 clinicians found the CFI feasible, acceptable and useful. Clinician feasibility ratings were significantly lower than patient ratings and other clinician-assessed outcomes. After administering one CFI, however, clinician feasibility ratings improved significantly and subsequent interviews required less time. Conclusions: The CFI was included in DSM-5 as a feasible, acceptable and useful cultural assessment tool. Declaration of interest R.L.-F., N.K.A. and L.J.K. receive royalties from an edited book on the Cultural Formulation Interview, published by American Psychiatric Publishing, Inc.