In this study, wall-modeled large-eddy simulation of transonic buffet phenomena over the OAT15A supercritical airfoil at two different Mach number conditions (nonbuffet M∞ = 0.715 and buffet M∞ = 0.73 conditions) at high Reynolds number Rec = 3.0 × 106 is conducted to investigate the prediction accuracy of the wall-modeled large-eddy simulation for the buffet phenomena. Thanks to the wall model, at the present Reynolds number, the grid spacing and the time-step size are increased by one order of magnitude compared with the traditional wall-resolved large-eddy simulation, and the high-fidelity large-eddy simulation can be applied to the buffet phenomena, which include the very low-frequency shock-wave oscillation. The results demonstrate the capability of the present wall-modeled large-eddy simulation for predicting the buffet phenomena. The present wall-modeled large-eddy simulation successfully predicts the buffet onset in the Mach number sweep, the buffet frequency, and turbulence statistics without the use of any ad hoc corrections. Instantaneous flow structures show that the present wall-modeled large-eddy simulation properly resolves the key flow features in the unsteady dynamics of the transonic airfoil buffet phenomena such as various scales of turbulent structures, generated acoustic waves, detailed shock-wave/boundary-layer interaction, and shock-induced flow separation.