This effort discloses a bioinspired methodology based on widespread polymer processing techniques for the fabrication of shell-mimicking structural poly(lactic acid) (PLA), one of the most important biodegradable polymers, but suffering from limited strength, toughness and heat resistance. The ordered, micro/nanostructural assembly consisting of a high-strength phase and tenacious interfacial ligaments was established in the shell-mimicking PLA by virtue of employing customized zinc oxide (ZnO) whiskers and intensive shear flow. Demonstration of the exceptional properties for the structured PLA is presented, outperforming normal PLA with nearly double the tensile strength (119.4 MPa) and over 2.5-fold improvement in impact toughness (11.5 KJ m−2), as well as the largely enhanced resistance to heat distortion and almost perfect UV light shielding efficiency. The high strength and toughness are unprecedented for PLA, and are in great need for structural applications.