Abstract: Polylactic acid (PLA) is a biodegradable polyester with broad application prospects, however, its practical utilization is limited by a low heat deflection temperature and inherent brittleness. Although blending with thermoplastic polyurethane (TPU) can enhance toughness, the poor compatibility between the two phases greatly restricts the further enhancement of properties and applications of the blended material. Therefore, the effect of maleic anhydride-grafted polyolefin elastomer (POE-g-MAH) on the properties of TPU/PLA (30/70 by weight) blends was systematically investigated. The morphological structure, crystallization behavior, thermal properties, and mechanical performance of the blends were comprehensively investigated by varying the POE-g-MAH content (0–10wt%) and employing a suite of characterization techniques, including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), heat deflection temperature (HDT) testing, and mechanical property measurements. The experimental results indicated that POE-g-MAH effectively enhanced the interfacial compatibility between PLA and TPU, as evidenced by a more homogeneous phase morphology observed in SEM images and a concomitant significant improvement in mechanical properties. Furthermore, this study establishes a clear correlation between the microstructure and macroscopic properties of the blends, thereby providing valuable theoretical insights and practical guidance for the future interface design and performance optimization of TPU/PLA blends. These findings contribute to advancing the application of high-performance bio-based plastics.