Abstract Social inequalities in mental health are evident in the prevalence of mental health problems, but also the utilisation and patents’ perceived benefits of treatment. However, the extent of these disparities on a global scale and whether there are country-level differences in the predictors of mental health service use remain unknown. This study uses data from the Wellcome Global Monitor 2020, a nationally representative survey encompassing 111 countries and 117,088 individuals. We examine the association of socio-economic factors (such as household income and education), psycho-social factors (including stigma perception and trust in health professionals), and country-level variables (such as GDP, Gini coefficient, and health expenditure) with mental health service use and perceived effectiveness of treatment. Multi-level logistic regression models were employed for analysis. The utilisation of mental health professions of people with depression or anxiety symptomology is higher in HICs (predicted probability of 62% CI[0.60 - 0.65]) compared to LIMCs (predicted probability of 33% CI[0.31 - 0.34]). Higher country GDP (OR = 1.26 CI[1.08-1.47]) and health expenditure (OR = 1.11 CI[1.04-1.19] per percentage of health expenditure) are associated with higher treatment utilisation. On the individual level, those in the wealthiest quintile are more likely to engage with mental health professionals (OR = 1.25[1.14-1.36]) and perceive this treatment as highly beneficial (OR = 1.23[1.07-1.40]). Trust in healthcare practitioners and perceived stigma are also associated with mental healthcare use. This analysis shows strong patterns of mental healthcare use and perceived benefits depending on the wealth of the country, health expenditure and individual socio-economic status. Moreover, disparities in treatment utilization and effectiveness are also influenced by trust in healthcare professionals and perceived mental health stigma.