This study investigates the potential use of sugarcane bagasse biochar as a sustainable modifier for asphalt binders. A neat asphalt binder (AC 50–70) and a biochar-modified binder containing 5% by weight of biochar were evaluated through rheological and chemical analysis. The rheological results showed that biochar addition increased the dynamic shear modulus and reduced the phase angle, indicating enhanced stiffness. The Multiple Stress Creep and Recovery (MSCR) test confirmed improved rutting resistance and higher recovery for the biochar-modified binder, although differences were within statistical variability. However, fatigue analysis using Linear Amplitude Sweep (LAS) test revealed a reduction in fatigue life and greater brittleness for the modified binder. Fourier-transform infrared spectroscopy (FTIR) results demonstrated that the addition of biochar mitigated short-term aging, with significantly lower increases in oxidation index (ICO and ISO) from the unaged to the aged biochar-modified binder compared to the neat binder. Overall, sugarcane bagasse biochar showed potential as an eco-friendly modifier capable of improving high-temperature performance and aging resistance, although further optimization is needed to mitigate its impact on fatigue resistance.