The new hybrid compound called propane-1,3-diammonium selenate-selenide tetrahydrate (PDASe) was obtained by slow evaporation and characterized by X-ray diffraction, NMR and IR spectroscopies, TGA and DSC analysis and UV–visible transmittance. This compound contains both SeIV in the form of selenide (SeO32−) trigonal pyramids and SeVI as selenate (SeO42−) tetrahedra. The structure is built up from tunnels containing all the components of the structure and oriented along b axis. The organic and inorganic groups are linked together by two types of hydrogen bonds, O–H⋯O and N–H⋯O. Crystal structure and Hirshfeld surfaces analysis revealed that the compound were mainly supported by N–H⋯O and O–H⋯O intermolecular interactions and the uncoordinated water molecules play a key role in the construction of the 3D stacking motif. The dehydration and the decomposition of the title compound are confirmed by the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The analysis by the UV visible spectroscopy confirmed the transparency of our compound in the visible region.