Environmental concerns associated with waste tires and plastic bottles have driven the adoption of recycling-based modifiers to enhance pavement performance. This study investigates the feasibility of utilizing Styrene–Butadiene Rubber (SBR) and Plastic Bottle Waste (PBW) as sustainable modifiers in Hot Mix Asphalt (HMA). Modified asphalt mixtures were prepared with PBW and SBR contents ranging from 2% to 10% by weight of the Optimum Binder Content (OBC). The performance of conventional and modified mixtures was evaluated using Marshall Stability, rutting resistance, Indirect Tensile Strength (ITS), and microstructural and chemical characterization through Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD). Results indicate that a 6% modifier content provides optimum performance enhancement, leading to significant improvements in stability, tensile strength, rut resistance, thermal stability, and stiffness. Microstructural analyses confirmed improved binder–modifier interactions and enhanced material compatibility. Comparatively, SBR demonstrated superior performance improvements over PBW, indicating its higher effectiveness as an asphalt modifier. In addition to mechanical benefits, the incorporation of SBR and PBW offers substantial environmental advantages by reducing landfill disposal and incineration, thereby lowering the associated carbon footprint. Overall, the findings support the use of recycled SBR and PBW as cost-effective, durable, and environmentally sustainable alternatives for producing high-performance asphalt mixtures, contributing to extended pavement service life and sustainable infrastructure development.