First-principle calculations within the framework of density functional theory are employed to study the electronic and half-metallic ferromagnetic properties of Be_1−x Cr _x S at concentrations x = 0.0625, 0.125, and 0.25 in zinc-blende phase. The calculations of electronic and magnetic properties reveal that Be_1−x Cr _x S is a half-metallic (HM) ferromagnet with 100 % spin polarization and HM gap. On the other hand, for the majority-spin states, the strong hybridization between 3 p (S) and the 3 d- t _2g (Cr) partially filled states dominates the gap and this stabilizes the ferromagnetic ground state associated with double-exchange mechanism, while the total magnetization is an integer Bohr magneton of 4 u _B that confirms the half-metallic behavior of Be_1−x Cr _x S compounds. Therefore, the chrome-doped beryllium sulfide (BeS) seems to be a potential candidate for spin injection in the field of spintronic applications.