The synergistic effect of divinylbenzene and triallyl cyanurate on the properties and structure of the thermoplastic vulcanizate prepared from a blend of polypropylene and hydrogenated styrene-butadiene-styrene triblock copolymer by vulcanization under dynamic conditions with 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane was revealed. The synergism consists in the enhancement of the strength, increase in the relative elongation, and decrease in the compression set to a greater extent then when using divinylbenzene or triallyl cyanurate separately. The synergism is caused by the increased gel fraction content and vulcanization network thickness, with preservation of the higher molecular mass of the polypropylene matrix.