In this study, the dynamic behavior of a flexible rotor system subjected to support excitation (imposed displacements of its base) is analyzed. The effect of an excitation on lateral displacements is investigated from theoretical and experimental points of view. The study focuses on behavior in bending. A mathematical model with two gyroscopic and parametrical coupled equations is derived using the Rayleigh-Ritz method. The theoretical study is based on both the multiple scales method and the normal form approach. An experimental setup is then developed to observe the dynamic behavior permitting the measurement of lateral displacements when the system’s support is subjected to a sinusoidal rotation. The experimental results are favorably compared with the analytical and numerical results.