In this study, new series of lanthanide 4,4′-oxybis(benzoates) of the general formula Ln₂oba₃·nH₂O, where Ln = lanthanides from La(III) to Lu(III), oba = C₁₂H₈O(COO) ₂ ²⁻ and n = 3–6, has been prepared under hydrothermal conditions. The compounds were characterized by elemental analysis, infrared spectroscopy, X-ray diffraction patterns measurements and different methods of thermal analysis (TG, DSC, and TG-FTIR). In addition, photoluminescence properties of the selected complexes have been investigated. Crystalline compounds are isostructural in the whole series. Both carboxylate groups are deprotonated and engaged in the coordination of Ln(III) ions. Heating of the complexes leads to the dehydration and next decomposition processes. Although of the same structure, the removal of water molecules proceeds in different ways. In the nitrogen atmosphere, they decompose releasing water, carbon oxides and phenol molecules. The complexes of Eu(III), Tb(III) and Dy(III) exhibit photoluminescence in the visible range, whereas the compounds of Nd(III) and Yb(III) in the near-infrared region upon excitation by UV light.