Reliable epidemiological data on the burden of mental disorders, key risk factors and access to health services is crucial in helping to design appropriate trauma-informed mental health and psychosocial support responses for the at least 1.6 million internally displaced persons (IDPs) in Ukraine. The aim of this study was to collect scientifically rigorous evidence on the mental health and psychosocial support needs of IDPs in Ukraine in order to help inform relevant policies and programmes. This study found a prevalence of post-traumatic stress disorder (PTSD) of 32% (22% men, 36% women), while the prevalence of depression was 22% (16% men, 25% women) and the prevalence of anxiety was 17% (13% men, 20% women). This study recommends that IDPs be considered as one of the target groups for mental healthcare provision by the relevant agencies in Ukraine. The findings support the need for a scaled-up, comprehensive and traumainformed approach to the provision of mental healthcare for IDPs in the country.