The paper evaluates the financial stability and efficacy of selected oil companies in the Republic of Croatia in the period from 2016 to 2020. The companies included in the analysis are INA d.d., Petrol d.o.o. and Crodux derivatives dva d.o.o. which were the three largest oil companies in the Republic of Croatia according to the categories of number of employees and of total revenues in 2019. Financial ratios showed that the business of the company INA d.d. were not at good levels, with the exception of debt to assets ratio which had favorable values due to increased own financing compared to other sources of financing. In the same period, the company Petrol d.o.o. operated extremely successfully achieving high rates of return to the owners of their own capital. Operations of the company Crodux deri vati dva d.o.o. can be rated as good according to most individual financial indicators, with the exception of debt to assets ratio. The application of Altman's Z-score model showed that in the company INA d.d. there is a high risk of bankruptcy, while in the companies Petrol d.o.o. and Crodux derivatives dva d.o.o. in most analyzed years, the risk of bankruptcy is negligible. Kralicek's DF indicator confirmed the assessment of the financial stability and performance of selected oil companies with a lower level of concern about bankruptcy. Summarizing the overall conclusions derived from the analysis, it can be concluded that the company Petrol d.o.o. is the most stable and successful oil company in the Republic of Croatia, as proved by the year 2020, in which, due to the global decline in demand for oil derivatives, the company performed better than during economic progress. Operations of the company Crodux derivati dva d.o.o. would be improved by more adequate management of assets and liabilities. The company INA d.d., in addition to the problems of liquidity, profitability and speed of asset circulation, operates with a high risk of bankruptcy and is slow to adapt to the situation on the oil market.