Ni2P@Carbon (Ni2P@C) yolk-shell nanocomposite have been synthesized through a phosphorization-in-nanooctahedron combined with an annealing strategy. As an anode material, the as-obtained Ni2P@C nanocomposite presents excellent lithium/sodium storage performance for lithium ion batteries (LIBs) and sodium ion batteries ( SIBs). The significantly enhanced electrochemical properties are attributed to the electrochemical conductivity of the carbon shell and the yolk-shell nanoarchitecture, which provides buffer space to remit the volume changes of Ni2P during cycles process, enlarges the contact area of electrolyte/electrode and shortens the diffusion path of Li+(Na+)/electrons. As the anode in LIBs, the Ni2P@C nanocomposite delivers a discharge capacity of 512.3 mA h g(-1) at 100 mA g(-1) after 100 cycles. The specific capacity could be still 398.1 mA h g(-1) at 1 A g(-1) even after 1000 cycles. As an anode for SIBs, the reversible capacity of the Ni2P@C nanocomposite is 291.9 mA h g(-1) at 100 mA g(-1) after 300 cycles. The enhanced performance of Ni2P@C nanocomposite electrode can be ascribed to the advantageous structural design.