Abstract: Working capital is one of the most important investment decisions of current assets as in fixed assets and funding policies run by the firm to achieve profitability and maximize the wealth of shareholders. This study aims to investigate the relationship between working capital, firm size and firm profitability. The samples of this study are manufacturing firms (e.g., food and beverage, cigarettes and cosmetics, and household appliances sector) which are listed on the Indonesia Stock Exchange (IDX) from the period 2010 to 2017. The data is processed and analyzed using Eviews 9. The results of the study reveal that working capital and firm size have a significant effect on firm profitability. Keywords: Working capital management, firm size, firm profitability