The oil pollution of seawater is an important problem especially for its toxicity on marine organisms and being a cover on surface water preventing the penetration of oxygen into sea water. In this paper oil pollution levels were determined in sea water and sediment samples of Tuticorin Bay near Thermal power plant. Three stations were fixed and oil concentrations were varied in examined area. The highest level found in station 1 near thermal power plant. Oil concentration was recorded maximum of 130.8 mg/L in surface water and sediment showed 86 mg/g in station 1. The studies revealed that the oil concentrations mainly depend on earlier ash dumpsite and water out fall from Thermal power plant.