IntroductionThe Partners for Change Outcome Management System (PCOMS) is a client feedback-system built on two brief visual analogue self-report scales. Prior studies of PCOMS have found effects varying from significant positive to negative. Aims of present study are; to test the predicted beneficial impact of PCOMS, while accounting for methodological flaws in prior studies and to clarify under which circumstances the addition of PCOMS to therapy has a beneficial effect.Methods and analysisThis study focuses on patients applying for brief, time-limited treatments. Four centres will be randomised to either treatment as usual (TAU) or TAU with PCOMS. All participating patients will be assessed four times. The full staff in the experimental condition will be trained in PCOMS. In the second part of this study, all therapists in the PCOMS condition will fill in a questionnaire concerning the influence of regulatory focus, self-efficacy, external or internal feedback orientation and perceived feedback validity of PCOMS. Finally, patients in the PCOMS condition will be asked to give feedback through a structured interview.The primary outcome measure is the Outcome Questionnaire over the period from beginning to end of therapy. The Mental Health Continuum-Short Form and Consumer Quality Index are also completed. In the primary analysis, outcomes of the two treatment conditions on treatment outcome, patient satisfaction, costs, drop-out and duration will be examined with a three-level (within patient, between patients and between therapists) multilevel analysis. The DSM-classification, sex, education level, age of each patient and therapist factors will be included as covariates.Ethics and disseminationThe Medical Ethics Committee of the University of Twente approved this study (K15-11, METC Twente). Data will be included from 1 January 2016 to 1 July 2019. Study results will be disseminated through peer-reviewed journals and conferences.Trial registration numberNTR5466; Pre-results.