This study investigates the effect of incorporating recycled polymethyl methacrylate (r-PMMA) into polylactic acid (PLA) and further modifications with a bio-based compatibilizer (epoxidized soybean oil [ESO]). Various PLA:r-PMMA ratios were evaluated, with and without ESO. Blending r-PMMA into PLA significantly influenced mechanical properties. The 10PLA90r-PMMA blend showed enhanced elongation at break (6.10%) and tensile toughness (1686 kJ/m3) compared to pure PLA (3.34% and 737 kJ/m3, respectively), addressing PLA's inherent brittleness. The 30PLA70r-PMMA composition exhibited a tensile strength (TS) of 51.44 MPa and significant tensile toughness (1237 kJ/m3). Thermal analysis revealed an increase in the glass transition temperature (Tg) with higher r-PMMA content, reaching 124°C for 100r-PMMA, and a decrease in crystallinity percentage from 68.17% (pure PLA) to 30.43% (50PLA50r-PMMA). Incorporating ESO into a 50 PLA50r-PMMA blend modified its properties. Adding 3 parts per hundred resins (phr) ESO improved elongation at break (5.68%) and tensile toughness (1302 kJ/m3) while reducing TS (35.03 MPa). At 6 phr ESO, flexibility was maximized with an elongation of 6.37%, but TS decreased to 26.89 MPa. These findings highlight the synergy between r-PMMA and ESO in enhancing PLA's performance for sustainable applications and balancing mechanical and thermal properties while addressing environmental challenges.