In this study, we present the syntheses of three chalcogenides, BaCeCuSe3, BaCeAgS3, and BaCeAgSe3, using the sealed-tube method. The single-crystal X-ray diffraction technique is employed to determine the structures of BaCeAgQ3 (Q = S/Se) for the first time. These isostructural Ag-containing compounds (space group: Cmcm) crystallize in the KCuZrS3 structure type. Rietveld refinement study of the BaCeCuSe3 sample confirms its orthorhombic Eu2CuS3 type structure (Pnma). The building blocks of these pseudo-two-dimensional structures are tetrahedral MQ4 (M = Cu/Ag) and octahedral CeQ6 polyhedra, which are conjoined to form ∞2[CeMQ3]2− layer. The optical absorption studies reveal the semiconducting nature of the BaCeMQ3 with bandgaps of 1.4(2) eV-1.5(2) eV consistent with their electronic structures calculated using DFT studies. The thermal conductivity (ktot) measurements showed extremely low ktot values (0.43–0.67 Wm−1K−1) for these samples at 773 K. Solar cells were fabricated with the chalcogenides and the highest efficiency of ∼4% was achieved with BaCeAgS3.