Although sodium-ion batteries (SIBs) show attractive advantages over current dominant lithium ion batteries (LIBs), they still face great challenges in addressing the issues of low capacity and poor cycling stability. We herein report the synthesis of a nanohybrid of ultrasmall NiS2 nanoparticles embedded in porous carbon nanofibers (NiS2NP/p-CNF), which is implemented by an electrospinning process accompanied by further sulfide treatment. The highly dispersed NiS2 nanoparticles, coupled with the highly conductive porous nanofiber structure, endow the hybrids with favorable properties and structure for reducing the effects of volume expansion, providing a fast mass transport channel, and facilitating electron transfer. Systematic electrochemical studies verify that NiS2NP/p-CNF, when studied as an SIB anode, exhibits high performance with an excellent specific capacity (500 mA h g-1 at 0.1 A g-1) and a competitive rate capability, maintaining 200 mA h g-1 at 2.0 A g-1, besides a long-term stability for 1000 cycles. The NiS2NP/p-CNF nanofibers provide a huge potential for the development of massive sodium storage.