The effects of (EAF) slag inclusion on the index and mechanical properties as well as cyclic properties of a clayey soil were investigated. Clayey soil was replaced with slag at 30%-50% and index, compaction, static and cyclic triaxial tests were conducted to obtain the mechanical properties of the slag admixed clayey soils. The liquid limit of mixtures decreased with the increasing amount of slag in the specimens. The maximum dry density increased by 20%, with the addition of slag. Under static isotropically consolidated undrained conditions, the internal friction angle of the specimens increased and the amount of cohesion reduced with an increase in the percentage of slag. Under a certain level of cyclic stress, the number of cycles required for liquefaction increased in slag admixed specimens. The cyclic shear modulus of the specimens increased to a 2.5 fold compared to the specimens without slag.