Mn oxide-loaded porous carbon nanofibers are prepared by electrospinning polyacrylonitrile nanofibers containing different amounts of Mn(CH₃COO)₂, followed by thermal treatments in different environments. It is found that the manganese salt may transform into γ-Mn(OOH)₂ or other Mn compounds during the thermal oxidation in air environment, while further thermal treatment in argon atmosphere results in MnO and Mn₃O₄ particles confined to a nanoporous carbon structure. Surface morphology, thermal properties and crystal structures are characterized using various analytical techniques to provide insight into the formation mechanism of the porous structure. These Mn oxide-loaded porous carbon composite nanofibers exhibit high reversible capacity, improved cycling performance, and elevated rate capability even at high current rates when used as anodes for rechargeable lithium-ion batteries without adding any polymer binder or electronic conductor.