Polystyrene (PS) has low impact strength and also shows poor strain hardening. In this work, poly(styrene-butadiene-styrene) triblock copolymer (SBS) was solution- and melt-blended with PS in the presence of a free-radical polymerization initiator, dicumyl peroxide (DCP), to enhance PS's thermal stability, mechanical properties, impact resistance, and strain hardening. The solution-blended PS/SBS containing 0.1% DCP annealed at 180 degrees C showed strong strain hardening, but the melt-blended PS/SBS annealed at the same temperature and time showed poor strain hardening. The change in the blending temperature, DCP concentration, and PS-to-SBS ratio had minimal effect on the strain hardening of melt-blended PS/SBS. The tensile strength increased with an increase in the concentration of DCP up to 0.1%, and beyond that level, the tensile strength started decreasing. The impact resistance considerably improved with an increase in the SBS loading in the PS matrix, and the enhancement was more than double of the impact resistance shown by the neat PS.