People with serious mental illness have higher morbidity and mortality rates compared with the general population. Mental health nurses are in an optimal position to address physical healthcare needs and inequalities experienced by this group. Research evidence suggests that mental health nurses may lack appropriate skills and confidence. The training needs of mental health nurses in physical health care of patients with serious mental illness and the perceived effectiveness of training that is provided to mental health nurses are explored in this review. A narrative synthesis approach (PROSPERO protocol registration ID=CRD42021230923) involved searching five electronic databases (PsycInfo, Cinahl, Embase, Medline and Web of Science) from 1990 to 2021. Study quality was assessed, and analysis and synthesis were initially deductively guided by a theoretical framework of training effectiveness prior to inductive data analysis. Eleven studies met the inclusion criteria. For studies examining perceived effectiveness of training, four themes were derived from the theoretical framework (individual trainee characteristics, work environment, learning outcomes, transfer of training to job) and further theme (service user factor) generated inductively. For studies examining training needs, three themes were derived inductively (knowledge and skills requirements, modality of training, service and healthcare factors). The study highlights the need for ongoing learning to improve practice. It also provides another perspective in terms of understanding the influence of service user factors (motivation and mental state) in designing and implementing of future training in mental health settings. [Abstract copyright: © 2023 The Authors. International Journal of Mental Health Nursing published by John Wiley & Sons Australia, Ltd.]