Electrochemical performance of Ni₂SnP was assessed in Li-ion and Na-ion battery systems. When cycled versus Li, Ni₂SnP exhibited a reversible specific charge of 700 mAh.g^-1 (theoretical specific charge: 742 mAh.g^-1). In the Na system, the specific observed charge was ca. 200 mAh.^g-1 (theoretical specific charge: 676 mAh.g^-1). X-ray diffraction, Ni K-edge X-ray absorption spectroscopy, and ³¹P and ⁷Li/²³Na nuclear magnetic resonance spectroscopy were used to elucidate the electrochemical mechanisms in both systems. Versus Li, Ni₂SnP undergoes a conversion reaction resulting in the extrusion of Ni and the alloying of Li-Sn and Li-P. On delithiation, the material partially recombines into a Sn- and Ni-deficient form. In the Na system, Ni₂SnP reacts through the conversion of P into Na₃P. These results indicate that the recombination of the pristine material (even partially) increases cycling stability.