OBJECTIVES The aim of this study was to measure income-related inequality in completed suicide across the provinces of Iran. METHODS This ecological study was performed using data from the Urban and Rural Household Income and Expenditure Survey-2010 conducted by the Iranian Center of Statistics, along with data on completed suicide from the Iranian Legal Medicine Organization in 2012. We calculated the Gini coefficient of per capita income and the completed suicide rate, as well as the concentration index for per capita income inequality in completed suicide, across the provinces of Iran. RESULTS The Gini coefficients of per capita income and the completed suicide rate in the provinces of Iran were 0.10 (95% confidence interval [CI], 0.06 to 0.13) and 0.34 (95% CI, 0.21 to 0.46), respectively. We found a trivial decreasing trend in the completed suicide incidence rate according to income quintile. The poorest-to-richest ratio in the completed suicide rate was 2.01 (95% CI, 1.26 to 3.22). The concentration index of completed suicide in the provinces of Iran was -0.12 (95% CI, -0.30 to 0.06). CONCLUSIONS This study found that lower income might be considered as a risk factor for completed suicide. Nonetheless, further individual studies incorporating multivariable analysis and repeated cross-sectional data would allow a more fine-grained analysis of this phenomenon.