Wild birds play an important role as a bio-indicator for heavy metals pollution in the environment due to its wide distribution and its higher trophic level in the food chain. In the present study, 46 Slender-billed Gulls (Larus genei) were collected during the breeding season from Lake Quaron protected area, Fayoum governorate, Egypt. Levels of Cadmium (Cd), Lead (Pb), Copper (Cu) and Zinc (Zn) were estimated in different tissues of slender-billed gulls (liver, breast muscle, heart and breast feathers). The aim of the current study is to determine the best tissue which can be used as a bio-indicator for each metal. Also to assess the environmental pollution with heavy metals in Lake Quaron. The result revealed that the higher concentration of Cd was estimated in the heart and liver (P<0.05) while the lower concentration was observed in feathers and muscle. The higher level of Pb and Zn were observed in feathers (P<0.05) and the lower level were observed in muscle. The major site of Cu accumulation in the examined tissue was liver (P<0.05) and the minor site was muscle and heart. Generally, the liver can be used as a good indicator for both Cd and Cu while feathers are a good indicator for Pb and Zn. The level of all the examined metals was relatively decreased in Lake Quaron except Zn was increased in comparison with a previous study.