This research study deals with the defining of dynamic behaviors of a portal frame structure with tapered members by using Finite Element Method (F.E.M.) and experimental modal analysis. Portal frame with three beam members is used in this study. Frame structure is composed by two tapered and one uniform cross sectioned beams. The first part of thesis is about the finite element modelling of the model which is developed in ANSYS. Theoretical modal analysis to find the natural frequencies and mode shapes of the frame is performed by using the finite element model. The second part of thesis is experimental modal analysis of the frame under study. For this purpose, the experimental modal test setup has been established. The modal parameters found from both numerical and experimental methods are compared and good agreement is found.