The crystal structure of the 2:1 sodium perchlorate · diethylene glycol complex has been determined by single crystal X-ray diffraction. It crystallizes in space group P21212 with a = 7.853(3), b = 7.900(2), c = 10.120(2) Å and Z = 2. Both the sodium ion and the diethylene glycol molecule are disordered, and were modeled with partial site occupancy factors. One sodium position is 7-coordinate and the other is 8-coordinate. The sodium perchlorate ions pack in layers parallel to  and , with the glycol molecules in channels between layers.