Single crystals of rare-earth selenate-selenite of composition: Nd₂(SeO₄)₂(SeO ₃) (H₂O) was obtained by interaction of amine-selenate monohydrate [NH₃(CH₂)₂NH ₂(CH₂)₂ NH₂(CH₂)₂NH₃ ]_0.5[SeO₄] .H₂O with Nd³⁺ ions followed by hydrothermal processing at 150^oC. The material crystallizes in the monoclinic space group P2₁/c with the following cell parameters: a = 10.608(2), b = 13.951(3), c = 9.799(3)Å, â= 93.12(2)^o. The infrared spectrum clearly shows the presence of coordinated water molecule. The absorption bands at 3508cm^-1 and 3348cm^-1 corresponds respectively to asymmetric and symmetric stretching vibrational modes of ligated water molecule. The absorption band at 1630cm^-1 is attributed to the bending vibrational mode of the aqua ligand. The absorption bands at 878, 913 and 962cm^-1 are assigned to õ_(Se-O) vibrations. The material is stable up to 180^oC. The first weight loss of 2.64% (Calc 2.56%) in the region 180-250^oC is indicative of the removal of one molecule of coordinated water. The second weight loss of 16.66 %(Calc16. 23 %) in the region 600-650^oC corresponds to the loss of SeO₂.