BACKGROUND: Evidence on the social determinants of mental health conditions and violence among people who inject or use drugs (PWUD) is limited, particularly in conflict-affected countries. We estimated the prevalence of symptoms of anxiety or depression and experience of emotional or physical violence among PWUD in Kachin State in Myanmar and examined their association with structural determinants, focusing on types of past migration (migration for any reason, economic or forced displacement). MATERIALS: A cross-sectional survey was conducted among PWUD attending a harm reduction centre between July and November 2021 in Kachin State, Myanmar. We used logistic regression models to measure associations between past migration, economic migration and forced displacement on two outcomes (1) symptoms of anxiety or depression (Patient Health Questionnaire-4) and (2) physical or emotional violence (last 12 months), adjusted for key confounders. RESULTS: A total of 406, predominantly male (96.8%), PWUD were recruited. The median age (IQR) was 30 (25, 37) years, most injected drugs (81.5%) and more commonly opioid substances such as heroin or opium (85%). Symptoms of anxiety or depression (PHQ4 ≥ 6) were high (32.8%) as was physical or emotional violence in the last 12 months (61.8%). Almost one-third (28.3%) had not lived in Waingmaw for their whole life (migration for any reason), 77.9% had left home for work at some point (economic migration) and 19.5% had been forced to leave home due to war or armed conflict (forced displacement). A third were in unstable housing in the last 3 months (30.1%) and reported going hungry in the last 12 months (27.7%). Only forced displacement was associated with symptoms of anxiety or depression [adjusted odds ratio, aOR 2.33 (95% confidence interval, CI 1.32-4.11)] and recent experience of violence [aOR 2.18 (95% CI 1.15-4.15)]. CONCLUSION: Findings highlight the importance of mental health services integrated into existing harm reduction services to address high levels of anxiety or depression among PWUD, particularly among those who have been displaced through armed conflict or war. Findings reinforce the need to address broader social determinants, in the form of food poverty, unstable housing and stigma, in order to reduce mental health and violence.