Transition-metal phosphides have been increasingly investigated because of their high theoretical specific capacity and low potential for sodium storage. Herein, we describe the development of Ni2P nanosheets on carbon cloth (Ni2P Ns/CC), which behaves as a flexible 3D anode for sodium-ion batteries. Such a Ni2P Ns/CC delivers a high capacity of 399 mA h g(-1) at 0.2 A g(-1) At 2 A g(-1), it still delivers 72 mA h g(-1) even after 1000 cycles. The impressive performance is attributed to such a self-supported structure. Moreover, a possible conversion reaction mechanism is also carefully revealed.