Fraxinus excelsior L. (Common Ash) is a deciduous tree that grows in wild and urban Turkey. Fraxinus excelsior has been tested as a possible biomonitor of heavy metals in the city of Kayseri, Turkey. Forty-eight sites (urban road side, road side, urban park, industrial, suburban and rural sites) in and around the city of Kayseri were investigated. In this study, the concentrations of Pb, Cd, Cu, Zn, Ni and Cr in unwashed and washed leaves and soils were determined. There were significant relationships between samples of the heavy metal concentrations from surface soil and washed leaves. The concentrations of heavy metals in the leaves of F.excelsior increased along with the urbanization of the sites. Fraxinus excelsior was found to be a useful biomonitor of the determined heavy metals.