The concentration of radon-222 in different brands of cooking oil samples was evaluated using a passive technique. Besides, the concentration of radium-226 and uranium-238 was calculated. Radiation hazard indices including the annual ingestion dose and excess cancer risk caused by the ingestion of radon were determined for all oil samples. The results demonstrated that activity concentrations of 222Rn, 226Ra, and 238U in all cooking oil samples were lower than the recommended values. A positive correlation was observed between radon concentrations and radium concentrations as well as radium concentrations and uranium concentrations in cooking oil samples. The maximum value of the annual ingestion dose calculated from the concentration of 222Rn is 131.417±6.933 nSv/y. Our results show that all the oil samples under this study do not create any cancer risk from ingestion of radon or other natural radionuclides through used cooking oil at these exposure levels and are safe for public health