In order to investigate copper, arsenic, lead and zinc contamination in topsoil of the Erdenet copper mining area in Mongolia, soil samples collected from the surrounding area were examined for trace element concentrations, geochemical fractions, and phase distributions. Fifteen locations (residential area; mine industrial area; control area; tailings dam) were sampled during all four seasons. Of the 19 trace elements determined, the highest concentrations of Cu (1443–4866 mg kg−1), As (26–52 mg kg−1), and Mo (24–49 mg kg−1) in soils from the mine industrial area exceeded the corresponding values listed in the National Standard of Mongolia. Soil samples were fractionated into five phases: exchangeable, carbonate bound, Fe/Mn oxide bound, organic matter bound, and residual. Copper was largely associated with the organic/sulphide fraction, and As, Pb and Zn were associated mainly with the residual and Fe/Mn oxide fractions. Significantly high enrichment factor (EF) and geoaccumulation index (Igeo) values confirmed that Cu and As in the soil from the mine industrial area reach serious levels and their sources may be related to anthropogenic activities such as mining.