Investigation of ErNi 2 Mn x with 0.90 ≤ x ≤ 1.10 indicates that the MgCu 2 -type structure (with space group Fd-3m) is formed within x = 0.97-1.10. Curie temperature T C  = 50 K of ErNi2Mn is significantly higher than those of the corresponding ErNi 2 (T C  = 7 K) and ErMn 2 (T C  = 15 K) compounds. Detailed analyses of DC magnetization data demonstrate that the magnetic phase transition at the Curie temperature is second order. The magnetic entropy change around T C has been found to be 4.8 J/kg K for a magnetic field change of 0 to 5 T with its relative cooling power ∼283 J/kg. ⁵⁷Fe Mössbauer spectra below T C have been fitted with three sub-spectra representing three inequivalent local magnetic environments while the paramagnetic spectra are fitted using two sub-spectra for two inequivalent crystal sites (8a and 16d), which supports the conclusion based on Rietveld refinement that Mn atoms occupy at both 8a and 16d sites.