This study investigates the effects of irradiation on the mechanical properties of dolomite-filled polypropylene (PP)/recycled polyethylene terephthalate (r-PET) composites across varying filler ratios. Composites with PP/r-PET ratios of 100/0, 90/10, 80/20, 70/30, and 60/40, each containing 3% dolomite, were subjected to irradiation doses of 0, 30, and 90 kGy. Tensile and impact tests, along with scanning electron microscopy (SEM) for surface morphology analysis, were employed to investigate performance changes post-irradiation. It is expected that the composite with a 90/10 PP/r-PET ratio at a 30 kGy dose will demonstrate the highest tensile and impact strengths, while increased irradiation doses are predicted to reduce mechanical properties across other ratios. For raw PP, elongation at break is anticipated to reach its peak post-irradiation, with the 90 kGy dose likely yielding the highest Young’s modulus. Morphologically, non-irradiated samples are expected to exhibit fewer microcracks and retain greater structural integrity. Overall, the study aims to elucidate how irradiation influences the enhancement or reduction of mechanical properties in these composites, dependent on composition and irradiation dose.