In order to shield the massive electromagnetic perturbations and meet the more and more stringent requirement for advanced electronic equipment, development of diverse, lightweight and high-performance electromagnetic interference (EMI) shielding materials is urgent but still challenging. Herein, the facile and green method which combines fused deposition modeling (FDM) 3D printing, ball milling and microwave (MW) irradiation tech­ nology was proposed to fabricate exfoliated graphene nanoplatelets (GNPs) incorporated liner low density polyethylene (LLDPE) nanocomposite lightweight parts with porous and complex geometry structure. FDM 3D printing possesses high flexibility for structure design, which can significantly broaden the application of ma­ terials in various fields. Benefiting from design of a unique porous lamellar structure, the printed LLDPE/GNPs nanocomposite parts can achieve a prominent EMI shielding effectiveness (SE) of ~32.4 dB (with thickness- normalized specific EMI SE (SSE/t) of 318 dB cm2/g) in the range of 8.2–12.4 GHz. This remarkable charac­ teristic is due to internal multiple reflections and absorption of electromagnetic (EM) waves. In addition, the specific FDM 3D-printed porous parts prepared by our strategy exhibit a relatively higher EMI SE at a lower density than those lightweight EMI shields in literatures. The use of MW irradiation technology improves me­ chanical properties, especially for the interfacial bonding strength between filaments. More importantly, this strategy is highly favorable for the fabrication of lightweight porous EMI shields with tailorable and optimized shape/structure, which could be expected to be applied in aerospace fields, portable electronic devices, smart devices and so on.