Iznik Lake, a freshwater lake surrounded by a fertile basin of land in NW Turkey, is deteriorating gradually depending upon the increment in loadings which is ascribed to the inputs from streams, agriculture, excessive irrigation, urbanization and industrial activities along the shore, and atmospheric deposition. The main scope of this study is to assess the content, distribution and ecological risk of the elements (Al, Fe, Mn, V, Cd, Co, Cr, Cu, Ni, Pb, As and Zn) in the surficial sediments collected from 25 sites in the Lake Iznik. Quantitative indices and sediment quality guidelines were used to evaluate the pollution status of metals. The resulting estimates reflected a natural environment of low to moderate degree of impaction, and an approximate contribution of geogenic and anthropogenic inputs, with some variations among the stations. The enriched concentrations of As and Mn could be depending on the thermogenic activity along the active faults bounding the lake. Multivariate analysis demonstrated that the sources of Al, Fe, Co, Cr, Zn and V, concentrated at near-shore stations, could be attributed to mixed (lithogenic/anthropogenic) sources via streams. The enriched concentrations of Cd, Cu, Ni and Pb observed at the deep stations, and their sources were attributed to the transported/deposited sediments and partly atmospheric deposition. Except Ni, the metal concentrations in the majority of sediment samples were believed to be safe for living organisms. Local governments must prepare rational environmental strategies and suitable drainage programs to decrease the level of contaminants that pollute the environment and to prevent the dramatic drop of the lake's water.