An apparatus for activating a catalyst of a hybrid vehicle may include: an engine including a plurality of cylinders, at least one intake valve and at least one exhaust valve, a variable valve apparatus adjusting lift and opening timing of the intake valve and exhaust valve, an integrated starter-generator, a driving information detector detecting driving information including a vehicle speed, a displacement of an accelerator pedal, and a displacement of a brake pedal, an exhaust gas purification apparatus, and a controller cutting off fuel supplied into the cylinder, opening the exhaust valve by using the variable valve apparatus during a suction stroke, and generating electrical energy through the integrated starter-generator when a regenerative braking condition of a hybrid vehicle is satisfied from the driving information detected by the driving information detector.