Several heavy metals vis., Ba, As, Co, Cd, Cr, Cu, Fe, Mn, Ni and Zn were estimated in the water, sediment and total of 144 fish samples from Isikli Lake during March 2009-February 2010. Fe has the highest concentrations in water as well as sediment among the studied metals. The heavy metal levels, except Cr in water were the highest in summer and winter, though lower than WHO standards. Generally higher metal levels were found in liver of Cyprinus carpio, while the lowest were determined in muscle tissue. Heavy metal levels in tissues of carp increased in summer and winter, but decreased in autumn and spring. Significant positive and negative relationships were found between heavy metal levels and fish size. Generally some of the results were above the limits for fish proposed by WHO, EC and TSE. This study shows that a potential danger may occur in the future depending on the agricultural development.