Flexible free-standing hierarchically porous carbon nanofibers embedded with ultrafine (∼3.5 nm) MoO₂ nanoparticles (denoted as MoO₂@HPCNFs) have been synthesized by electrospinning and subsequent heat treatment. When evaluated as a binder-free anode in Li-ion batteries, the as-obtained MoO₂@HPCNFs film exhibits excellent capacity retention with high reversible capacity (≥1055 mA h g⁻¹ at 100 mA g⁻¹) and good rate capability (425 mA h g⁻¹ at 2000 mA g⁻¹), which is much superior to most of the previously reported MoO₂-based materials. The synergistic effect of uniformly dispersed ultrasmall MoO₂ nanoparticles and a three-dimensionally hierarchical porous conductive network constructed by HPCNFs effectively improve the utilization rate of active materials, enhance the transport of both electrons and Li⁺ ions, facilitate the electrolyte penetration, and promote the Li⁺ storage kinetics and stability, thus leading to a greatly enhanced electrochemical performance.