Clinical supervision is a psychologically safe practice that aims to provide support and training for workers within the healthcare industry, including mental health nurses. Over the years, clinical supervision has been cited as a practice to improve workforce outcomes for both individual mental health nurses and the organisations they work in. The aim of this scoping review is to examine the evidence exploring the relationship between clinical supervision and workforce outcomes for mental health nurses. Twenty-eight articles sourced from six databases were included in this study. The most frequently evaluated workforce outcomes were competence (n = 14), workplace culture (n = 13) and compassion (n = 7). Studies reported that the association between clinical supervision and workforce outcomes was predominantly positive, but there were mixed results for competence, workplace culture, job satisfaction and burnout. Details on the type of clinical supervision received by participants were limited, and most of the evidence included in this review included qualitative research and participants self-reporting their perceived benefits from clinical supervision, as opposed to using validated instruments in experimental and/or longitudinal study designs. Organisations should be hesitant to implement mandatory clinical supervision within workplaces, as this could have the opposite effect on workforce outcomes for mental health nurses who are already time-poor and overworked, as well as those who are indifferent or hostile to clinical supervision.