Heavy metal concentrations in surface water, wastewater and sediments collected from Mighan Lake in Markazi province, Iran were analyzed, and assessment contamination were evaluated according to the water and sediment quality guidelines. The results showed that the average concentrations of heavy metals in water were ranked as: Ni> Cr> Pb> Fe> Cu> Zn. In comparison with results the background values, the Mighan Lake was polluted by Ni, Cr, Pb and Fe, Most of metals might be mainly from industrial effluent and wastewater around the lake. In the sediments in the Mighan Lake, Fe, Ni, Pb and Cr showed a decreasing trend while Cu and Zn present an increasing trend. The increase of Cu and Zn might due to industrial activity around of Mighan Lake. The analysis of assessment contamination based on quality guidelines suggested that heavy metals in most water and sediments from the Mighan Lake had high toxicity, with Ni, Cr and Pb in water and moderate toxicity, with Zn and Cu in sediment being the highest priority pollutant.