This study compares a polymer-modified bitumen containing a biogenic component (“PMB-EXT”) with an unmodified bitumen (“Neat”) and a conventional polymer-modified bitumen (“PMB”), using the same mix design while varying only the binder. The three mixtures were characterized through dynamic modulus and cyclic fatigue tests according to the Simplified Viscoelastic Continuum Damage (S-VECD) theoretical-experimental framework, as well as through Stress Sweep Rutting tests based on the viscoplastic shift model. The results show that PMB-EXT ensures better fatigue performance than conventional PMB mainly due to reduced stiffness and increased toughness. Instead, the rutting performance of PMB-EXT is not as good as that of PMB but remains significantly better than that of the unmodified bitumen. Therefore, PMB-EXT could be effectively used, especially in pavements where cracking is the predominant distress, potentially outperforming conventional PMB.