Background There is limited evidence for the acceptability of training for mental health professionals on service user- and carer-involved care planning. Aim To investigate the acceptability of a co-delivered, two-day training intervention on service user- and carer-involved care planning. Methods Community mental health professionals were invited to complete the Training Acceptability Rating Scale post-training. Responses to the quantitative items were summarized using descriptive statistics (Miles, ), and qualitative responses were coded using content analysis (Weber, ). Results Of 350 trainees, 310 completed the questionnaire. The trainees rated the training favourably (median overall TARS scores = 56/63; median 'acceptability' score = 34/36; median 'perceived impact' score = 22/27). There were six qualitative themes: the value of the co-production model; time to reflect on practice; delivery preferences; comprehensiveness of content; need to consider organizational context; and emotional response. Discussion The training was found to be acceptable and comprehensive with participants valuing the co-production model. Individual differences were apparent in terms of delivery preferences and emotional reactions. There may be a need to further address the organizational context of care planning in future training. Implications for practice Mental health nurses should use co-production models of continuing professional development training that involve service users and carers as co-facilitators.