In this work, the authors studied the effects of electron beam (EB)-induced changes in stress-strain characteristics, heat shrinkage stresses, and structure characteristics on polypropylene (PP) composites containing bisphenol-A-dimethacrylate (BPDMA) as the radiation sensitizer and different contents of multi-walled carbon nanotube (CNT) filler (0–2 wt.%). The effect of stearic acid (SA) as the surface modifier on the improvement of CNT dispersion in the PP matrix was also studied. Initially, PP blends with different contents (up to 10 wt.%) of BPDMA were prepared to determine the effective concentration of the sensitizer for the modification of the PP matrix. PP/BPDMA composites and blends filled with CNTs were irradiated up to 25–50 kGy of radiation doses. The properties of unirradiated compositions and those modified by EB, were compared. Radiation-induced changes were confirmed by gel fraction and by the changes in Fourier transform infrared spectroscopy spectra. The results showed an increase in Young’s modulus, yield strength, and thermal-relaxation stresses for the irradiated PP/CNT compositions grafted with 3 wt.% of BPDMA and compatibilized with SA.