The study was aimed to evaluate effectiveness of utilizing a self-cementing fly ash derived from combustion of lignite at Afsin Elbistan thermal power plant in stabilizing a fine grained clayey soil (CL). Grain size and Atterberg limits analysis, compaction and triaxial compression tests were carried out on the clayey soil samples (pure soil) and also the samples of soil mixtures added various percentage of fly ash were prepared. The samples were used for triaxial compression test at optimum moisture contents determined by standard proctor test. The test results revealed denote that the shear strength of soil increases considerably with both addition of fly ash and curing time. Furthermore, the fly ash treatment and curing process brings also soil in more granular nature due to flocculation of the clay particles by cementation. It is clearly seen that Afsin Elbistan power plant fly ash is a very suitable material for improving of fine grained cohesive soils. Furthermore, utilization of Afsin Elbistan fly ash in soil stabilization was determined a positive influence on the environment and the economy.