We used the full-potential linearized augmented plane-wave method within the density functional theory framework to investigate the structural, elastic, electronic and magnetic properties of the rock-salt (B1) Sr0.75Mn0.25X (X = S, Se and Te). The Wu-Cohen generalized gradient approximation (WC-GGA) was used to describe the exchange-correlation potential. To get appropriate results about the electronic properties of Sr0.75Mn0.25X (X = S, Se and Te) alloys, the Tran-Blaha modified Becke-Johnson (TB-mBJ) potentials were also used. The experimental, theoretical results and our optimized equilibrium structural parameters are in good accord. Our elastic constants Cij were used to calculate the bulk modulus B, shear modulus S, Young’s modulus Y, Poisson's modulus ν, Pugh's ratio, acoustic velocities, and Debye temperature. It is confirmed that these compounds have brittleness and mechanical stable. Electronic properties like the spin polarized band structure and electronic density of state, and charge density were carefully examined. The calculated band structures reveal that the analyzed materials are semiconductors ferromagnetic behavior. Moreover, a study of the magnetic properties of Sr 0.75Mn 0.25X (X = S, Se and Te) compounds indicates that the value of the total magnetic moment for each compound is approximately 5μB.