This study aims to provide the mass balance of mercury and an assessment of anthropogenic mercury release into the air, water, wastes, and products from two oil refinery plants in Korea. The mercury concentrations in input streams (crude oil and condensates) and output streams (petroleum products and by-products, such as fly ash, sludge and waste water, and flue gas) were measured at two representative oil refineries. After normalizing the measured data at low recovery rates, facility A was found to release the most mercury through products, sludge, and air at 77.9%, 8.3%, and 8% respectively, and facility B released the most mercury through products, sludge, and air at 44.8%, 37.6%, and 11.1% respectively. The average national emission factor of mercury into the air from oil refineries was estimated at 0.12 mg-Hg ton−1 input product. The average mass distribution factors of mercury by oil refinery processes into petroleum products, by-products, and the air was 61.35%, 29.08%, and 9.56%, respectively.