Correct buckling strength calculation of stiffened panels leads to effective ultimate strength analysis. Under this point of view, the nonlinear buckling behavior of different stiffened panels is examined. Firstly, a series of finite element eigenvalue analysis has been carried out to determine the bucking mode shapes of stiffened panels. Then, a nonlinear finite element analysis was carried out by considering initial imperfections in order to investigate the effects of stiffener type and several geometric parameters on the buckling behavior of the stiffened ship panels. Beside this, the effects of lateral pressure on the nonlinear buckling behavior of the stiffened panels were also investigated. It is observed that the stiffener type has a great effect on the nonlinear buckling behavior of the stiffened ship panels. Tee bar stiffeners increase the stiffness of panels more than angle bar and flat bar stiffeners.