The possibility of half-metallic ferromagnetism in MgS doped with 12.5% concentration of C, Si, Ge and Sn was carried out by means of full-potential linearized augmented plane wave (FP-LAPW) method. The Generalized Gradient Approximation (GGA) and Local Spin Density Approximation (LSDA) were used for exchange-correlation corrections. The LSDA calculation shows that only C- doping induces half-metallic ferromagnetism and Si- doping shows nearly ferromagnet in MgS others do not exhibit ferromagnetism. However, GGA calculation shows C- doping shows nearly half-metallic property, Si- and Ge- doping exhibit ferromagnetism. While Sn- cannot induce ferromagnetism in host material. The ferromagnetism mainly arises from spin polarization of 2p states of dopant.