Background: It has been suggested that illness perceptions in mental health are related to treatment outcomes. Aims: We aimed to develop a short generic questionnaire to assess clients' problem perceptions in mental health, congruent with the Illness Perception Questionnaire (IPQ) for somatic health. Methods: We adapted the IPQ-R (Moss-Morris, R., Weinman, J., Petrie, K. J., Horne, R., Cameron, L. D., & Buick, D. (2002). Psychology and Health, 17, 1-16) to psychological complaints, in particular the IPQ-R's scales that assess clients' perceptions of what their problem actually is and what its causes are. We administered our adapted instrument, the IPQ-MH, to large groups of mental health clients, and subsequently performed psychometric analyses over the scores. Results: The identity scale of the IPQ-MH differentiates different clients; the structure scale of the IPQ-MH replicates that of the original IPQ-R; the cause scale reliably measures clients' attributions of causes to their mental problems. Conclusions: We conclude that our IPQ-MH can reliably assess clients' mental health problem perceptions.