Abstract The incorporation of magnetism to a solid material may drastically alter its electrical transport behavior, providing a way to modify the magneto-optoelectronic and thermoelectric features that have recently drawn a lot of scientific attention. In this regard, we utilized density function theory (DFT) based full potential linearized augmented plane wave (FP-LAPW) approach to study doping effect of Mn on physical characteristics of barium selenide (BaSe). Pristine BaSe is nonmagnetic semiconductor with indirect bandgap of 2.11 eV. Concentration dependent Mn doping in BaSe introduces spin polarized intermediate bands in the vicinity of Fermi level primarily composed of Mn-3d orbitals. Asymmetric band profiles indicate the ferromagnetic semiconductor nature of of Mn doped BaSe compounds. Total magnetic moment value of 5.0 μ _B, 10.0 μ _B, and 20.0 μ _B are obtained for corresponding Ba_1−xMn_xSe (x = 6.25%, 12.5%, 25%) systems. Furthermore, the analysis of optical and thermoelectric characteristics reveals the importance of studied alloy for application in advanced technologies including low energy light absorbers and thermoelectric generators.