Reactive compatibilization of poly (lactic acid) (PLA)-based polymer blend nanocomposites exhibit tremendous merits of biodegradability and high-performance towards commercial criteria, but the inferior crystallinity as well as the accompanied poor thermal stability impede its practical exploitation. In this work, we demonstrate that the interfacial positioned nanorods containing dual-grafts result in simultaneous “interfacial compatibilization” and “interfacial nucleation” in the fully biodegradable PLA/poly butylene succinate (PBSU) blend nanocomposites. The dual-grafted AlOOH containing both PBSU and poly (d-lactic acid) (PDLA) grafts (AlOOH-g-(D&B)) were pre-made and incorporated into the PLLA/PBSU blend. During melt compounding, AlOOH nanorods were selectively bridged at the PLLA-PBSU interface, facilitating both physical entanglement (PBSU-grafts within PBSU phase) and stereocomplex formation (PDLA-grafts within poly (l-lactic acid) (PLLA) phase). The unique interfacial architecture with both nanorods and stereocomplex crystals induces the refined morphology, rapid crystallization, and enhanced thermal resistance of the fully biodegradable polymer blend nanocomposites.