Investment is one of the most key macroeconomic variables and is influenced by factors such as monetary and financial, political and structural variables. The main purpose of this research is to investigate the factors affecting investment in the upstream sector of international oil companies, and the question arises as to what factors affect investment in international oil companies. Also, in addition to investment, factors affecting "exploration" and "development" have also been examined. These factors include oil price, gas price, carbon dioxide price, oil and gas reserves, interest rate, ratio of reserves to production and cumulative discoveries. For this purpose, four major international oil companies including BP, Total, Shell and Eni were investigated in the period of 2000-2021. The data were extracted from the annual reports of the mentioned companies and estimated using the panel data method. According to the results of the estimations, the price of oil has a positive and significant effect, and the price of carbon dioxide and the interest rate have a negative and significant effect on investment, development and exploration in international companies.