INTRODUCTION: Developed in dialogue with WHO, this research aims to incorporate lived experience and views in the refinement of the International Classification of Diseases Mental and Behavioural Disorders 11th Revision (ICD-11). The validity and clinical utility of psychiatric diagnostic systems has been questioned by both service users and clinicians, as not all aspects reflect their lived experience or are user friendly. This is critical as evidence suggests that diagnosis can impact service user experience, identity, service use and outcomes. Feedback and recommendations from service users and clinicians should help minimise the potential for unintended negative consequences and improve the accuracy, validity and clinical utility of the ICD-11. METHODS AND ANALYSIS: The name INCLUDE reflects the value of expertise by experience as all aspects of the proposed study are co-produced. Feedback on the planned criteria for the ICD-11 will be sought through focus groups with service users and clinicians. The data from these groups will be coded and inductively analysed using a thematic analysis approach. Findings from this will be used to form the basis of co-produced recommendations for the ICD-11. Two service user focus groups will be conducted for each of these diagnoses: Personality Disorder, Bipolar I Disorder, Schizophrenia, Depressive Disorder and Generalised Anxiety Disorder. There will be four focus groups with clinicians (psychiatrists, general practitioners and clinical psychologists). ETHICS AND DISSEMINATION: This study has received ethical approval from the Coventry and Warwickshire HRA Research Ethics Committee (16/WM/0479). The output for the project will be recommendations that reflect the views and experiences of experts by experience (service users and clinicians). The findings will be disseminated via conferences and peer-reviewed publications. As the ICD is an international tool, the aim is for the methodology to be internationally disseminated for replication by other groups. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov: NCT03131505.