The use of corrosion inhibitors is crucial for protecting oil and gas facilities. Furan and its derivatives are under investigation and have been proven to be effective as corrosion inhibitors. In this work, furan derivative (2-Acetylfuran) was studied as a corrosion inhibitor to protect mild steel in a pH 5.5 solution saturated with CO2. The results showed that a protection percentage of 92% can be achieved by 3 ppm of 2-Acetylfuran alone on mild steel. However, by adding 3 ppm of sodium thiosulfate pentahydrate to the solution, this percentage increases to 99.7%. At higher dosages of 2-Acetylfuran, the corrosion rate may increase due to the formation of acetic acid near the mild steel surface and increased hydrogen evolution. The increase in protection by the addition of sodium thiosulfate pentahydrate may be related to the formation of iron sulfide on the mild steel samples.