The first-principle methods of density functional theory were used to investigate the doping effect of 3d chromium (Cr) impurities on the electronic properties and the ferromagnetic arrangement of (BaO) barium oxide such as Ba_1−xCr_xO compounds at concentrations x = 0.25, 0.5, and 0.75. The p–d exchange coupling between 2p states of oxygen (O) and 3d (Cr) partially filled levels induces magnetism in the Ba_1−xCr_xO compounds. The majority- and minority-spin states exhibit respectively metallic and semiconducting features, leading to a half-metallic (HM) character with 100% spin polarization for all concentrations. The Ba_0.75Cr_0.25O, Ba_0.5Cr_0.5O, and Ba_0.25Cr_0.75O compounds have integral total magnetic moments of 4 μB per Cr atom with HM gaps of 0.055, 0.218, and 0.308 eV, respectively. These behaviors form accurate half-metallic ferromagnets and make Ba_1−xCr_xO as potential materials for possible spintronics applications.