We report the synthesis of black-colored crystals and a polycrystalline phase of BaSb2Se4 by high-temperature reaction of elements at 1173 ​K and 973 ​K, respectively. The X-ray diffraction studies show that it crystallizes in the monoclinic P21/c space group, and the structure is composed of one-dimensional stripes of ∞1[Sb2Se4]2− that are separated by the Ba2+ cations. The optical absorption study reveals the semiconducting nature (Eg ​= ​1.3(1) eV) of the polycrystalline BaSb2Se4 sample. A thermal conductivity (κ) study shows a gradual decrease of the κ-value from ∼0.39 ​W/mK to ∼0.29 ​W/mK on heating the polycrystalline sample from 300 ​K to 773 ​K. The DFT study of the electronic structure of BaSb2Se4 shows that the bandgap is indirect with a magnitude in the range of ∼1.0–1.6 ​eV depending on the choice of XC functional. The COHP analysis has been performed to investigate the relative strengths of chemical bonding between pertinent atoms in the BaSb2Se4 structure. © 2022 Elsevier Inc.