ObjectiveTo develop a core set of outcomes to be used in all future studies into discharge from acute mental health services to increase homogeneity of outcome reporting.DesignWe used a cross-sectional online survey with qualitative responses to derive a comprehensive list of outcomes, followed by two online Delphi rounds and a face-to-face consensus meeting.SettingThe setting the core outcome set applies to is acute adult mental health.ParticipantsParticipants were recruited from five stakeholder groups: service users, families and carers, researchers, healthcare professionals and policymakers.InterventionsThe core outcome set is intended for all interventions that aim to improve discharge from acute mental health services to the community.ResultsNinety-three participants in total completed the questionnaire, 69 in Delphi round 1 and 68 in round 2, with relatively even representation of groups. Eleven participants attended the consensus meeting. Service users, healthcare professionals, researchers, carers/families and end-users of research agreed on a four-item core outcome set: readmission, suicide completed, service user-reported psychological distress and quality of life.ConclusionImplementation of the core outcome set in future trials research will provide a framework to achieve standardisation, facilitate selection of outcome measures, allow between-study comparisons and ultimately enhance the relevance of trial or research findings to healthcare professionals, researchers, policymakers and service users.