The elastic, magnetic and electronic properties of MFe 3 N (M=Fe, Ru, Os) are investigated via first-principles calculations. The calculated results are in agreement with the experimental and other theoretical data. The high ratios of bulk modulus to shear modulus 2.7, 2.0, and 1.8 for γ′-Fe 4 N, RuFe 3 N, and OsFe 3 N, respectively, indicate that they have good ductility. γ′-Fe 4 N possesses the largest B/C 44 (3.41) ratio, which suggests that it is much prone to shearing. The net magnetic moment per formula unit decreases from 9.90 for γ′-Fe 4 N, 7.66 for RuFe 3 N, to 6.80μ B for OsFe 3 N.