BACKGROUND The Mini-International Neuropsychiatric Interview-Plus (mini-Plus) is a widely used diagnostic tool, yet research on the psychometric properties is limited. AIM To investigate the inter-rater reliability of the mini-Plus and to explore the concordance between mini-Plus diagnoses and clinician-rated diagnoses. METHOD mini-Plus interviews were conducted with psychiatric outpatients and recorded using audio and video devices. Independent raters, blind to the assessments of the first raters, assessed the recordings in order to investigate the inter-rater reliability. To examine the degree of concordance between the mini-Plus and the clinician, the diagnoses of the original interview and the clinical diagnoses were compared. RESULTS The inter-rater reliability was excellent for most diagnostic categories. A low correlation between the mini-Plus diagnoses and the clinician-rated diagnoses was found. CONCLUSION This study confirmed the excellent inter-rater reliability of the instrument, although some modules could be further improved. The consensus between mini-Plus diagnoses and clinician-rated diagnoses is limited. The mini-Plus can therefore supplement information collected by clinicians and may help prevent clinicians from missing important information.