This study aims to explain the effect of firm size, financial leverage and profitability both simultaneously and partially on income smoothing. The population in this study is the mining and agricultural companies of the IDX in 2017-2019. The sampling method used purposive sampling, as many as 33 companies passed the research criteria. The data source used in this study is secondary data in the form of annual financial reports. The data analysis technique used is multiple linear regression analysis. The results of the analysis in this study indicate that firm size and profitability have a significant positive effect on income smoothing, financial leverage has no significant positive effect on income smoothing. Meanwhile, simultaneously firm size, financial leverage and profitability have a significant effect on income smoothing.