Multifunctional applications including efficient microwave absorption and electromagnetic interference (EMI) shielding as well as excellent Li-ion storage are rarely achieved in a single material. Herein, a multifunctional nanocrystalline-assembled porous hierarchical NiO@NiFe₂O₄/reduced graphene oxide (rGO) heterostructure integrating microwave absorption, EMI shielding, and Li-ion storage functions is fabricated and tailored to develop high-performance energy conversion and storage devices. Owing to its structural and compositional advantages, the optimized NiO@NiFe₂O₄/15rGO achieves a minimum reflection loss of −55 dB with a matching thickness of 2.3 mm, and the effective absorption bandwidth is up to 6.4 GHz. The EMI shielding effectiveness reaches 8.69 dB. NiO@NiFe₂O₄/15rGO exhibits a high initial discharge specific capacity of 1813.92 mAh g⁻¹, which reaches 1218.6 mAh g⁻¹ after 289 cycles and remains at 784.32 mAh g⁻¹ after 500 cycles at 0.1 A g⁻¹. In addition, NiO@NiFe₂O₄/15rGO demonstrates a long cycling stability at high current densities. This study provides an insight into the design of advanced multifunctional materials and devices and provides an innovative method of solving current environmental and energy problems.