<p>Poly(butylene adipate-co-terephthalate) (PBAT) and thermoplastic starch (TPS) blends are promising biodegradable materials owing to their complementary properties. However, their practical application is severely limited by the inherent immiscibility between PBAT and TPS, which leads to poor interfacial adhesion, pronounced phase separation, and reduced flexibility. To address these challenges, this study introduces a simple and scalable two-step blending strategy to prepare chain-extended compatibilizer with block-like functionality using hexamethylene diisocyanate (HDI), and investigates their effects on the performance of PBAT/TPS blends. In the first blending step, compatibilizers with different architectures, namely non-chain (NC) and chain-extended compatibilizer with block-like functionality (BC), were prepared and comparatively evaluated. The results demonstrate that BC compatibilizers markedly improve the morphological, rheological, and mechanical properties of PBAT/TPS blends compared to NC counterparts. The enhanced performance is attributed to improved interfacial interactions, where the chain-extended compatibilizer with block-like functionality facilitates effective anchoring at the PBAT/TPS interface, thereby suppressing phase separation. Notably, the incorporation of 5 phr of the BC compatibilizer resulted in more than a two-fold increase in elongation at break, indicating a substantial enhancement in flexibility. Furthermore, the introduction of the BC compatibilizer did not adversely affect the degradation behavior of the blends. These findings highlight the potential of chain-extended compatibilizer with block-like functionality prepared via simple blending process as an effective strategy to overcome immiscibility in PBAT/TPS systems. By simultaneously enhancing mechanical performance while preserving biodegradability, this work provides a practical and sustainable approach for designing biodegradable materials suitable for industrial applications.</p> Graphical Abstract <p></p>