The dynamic behavior of buildings can change during construction stages. The brick walls cause a considerable effect on the modal behavior depending on the wall configuration. In this paper, it is aimed to present the effects of construction stages (bare frame, brick-walled and coated cases) on the modal parameters of reinforced concrete (RC) buildings. For this purpose, a three-storey RC building model with a 1/2 scale was constructed in the laboratory of Civil Engineering Department at Karadeniz Technical University. The modal testing measurements were performed by using operational modal analysis method for the bare frame, brick walled and coated cases of the building model. Randomly generated loads by impact hammer were used to vibrate the building model; the responses were measured by uni-axial seismic accelerometers as acceleration. The building's modal parameters at these construction stages were extracted from the processed signals using the enhanced frequency domain decomposition technique. The natural frequencies of the building model varied depending on the construction stages considerably. The frequencies decreased by increasing number of stories. But the brick walls caused a significant increase in the natural frequencies and affected the modal behavior that the longitudinal response occurred at first mode.