BACKGROUND: The current moment is characterised by deep-rooted uncertainties, such as climate change and COVID-19. Uncertainty has been reported to be associated with negative mental health outcomes, such as stress and anxiety. However, no comprehensive review on the association between uncertainty and mental health exists. AIM: The aim of the current scoping review was to systematically explore and describe the literature on the link between uncertainty and mental health. METHODS: A scoping review was undertaken following guidelines by Arksey and O'Malley (2005). RESULTS: One hundred and one papers addressing the association between uncertainty and mental health were identified. Most were cross-sectional studies (67%) conducted in the fields of medicine or nursing (59%), in high-income countries, among adult populations (74%), and in medical settings. Substantial heterogeneity was identified in the measurements of uncertainty and mental health. Most studies (79%) reported a positive association between uncertainty and mental health problems. CONCLUSIONS: Research is needed in more diverse contexts and populations. More robust designs are required to provide insight into the directionality and strength of the association between uncertainty and mental health. Few studies reported how individuals coped with uncertainty. Future studies should address the identified gaps and investigate interventions to address uncertainty and its determinants.