Disclosed is a hybrid brake system to perform a braking operation for a vehicle by generating hydraulic pressure in a master cylinder. The hybrid brake system includes an input shaft, a pedal simulator connected to the input shaft, a master cylinder provided therein with first and second pistons, an oil supply part supplying oil to the pedal simulator and the master cylinder, a power piston connected to the first piston, and a first chamber formed between the power piston and an inner surface of the master cylinder. The pedal simulator includes a simulation housing, a simulation rod provided at one end of the simulation housing, a second chamber formed at a lateral side of the first chamber to receive the simulation rod, and a boosting part communicated with the second chamber to generate the repulsive force as the brake pedal is pressed.