It is a well-identified fact that more elaborate laboratory studies should be carried out for evaluation of dynamic properties of different types of soils. Regardless of the mechanisms affecting the mechanical behaviour of the soils, past studies reveal that existence of fiber positively affects the strength of either cohesive or non-cohesive soils. A short literature survey provides numerous studies on the stress-strain behaviour of fine/coarse soils, reinforced by polypropylene fiber. On the other hand, studies concerning fiber reinforced soils subjected to dynamic loading are relatively rare. Therefore, in this research it was intended to investigate the effects of polypropylene fiber inclusion on the dynamic behavior of a clayey sand soil, within an experimental framework. In this scope, a number of cyclic triaxial compression tests were conducted to assess the effect of fiber presence. The effects of fiber length and content were experimentally evaluated. Hence, the variation of shear modulus ratio and damping ratio values by shear deformation was plotted to observe the effects of fiber length and inclusion level as well. The results are presented along with detailed evaluations.