Income smoothing is basically a management strategy to reduce fluctuating income levels. This study aims to determine the effect of company size, leverage and profitability on income smoothing in companies listed on the LQ45 Index of the Indonesia Stock Exchange for the 2017-2019 period. It was carried out on companies listed on the LQ45 Index of the Indonesia Stock Exchange in 2017-2019. Sampling was conducted by utilizing purposive sampling and obtained 11 companies, from which 33 data were collected. The analysis technique used was multiple linear regression analysis. Results showed that company size, leverage and profitability simultaneously can affect income smoothing of a company. Company size and profitability partially have a positive effect on income smoothing, while leverage has a negative effect on income smoothing.