In an attempt to better understand the properties of energetic eutectic materials, the eutectic mixture of hydrazine nitrate (HN) and nitroguanidine (NQ) was prepared by a melt crystallization method. The melting temperature and fusion enthalpy of the pure components and the eutectic were determined using differential scanning calorimetry. The structure of the HN-NQ title compound was characterized by infrared spectroscopy (IR), X-ray diffraction (XRD), and scanning electron microscopy. Thermodynamic functions such as excess Gibb's energy, excess enthalpy, and excess entropy of the title mixture were calculated using activity coefficient data. The intermolecular interactions of different molar ratios of the HN-NQ eutectic were determined by density functional theory (DFT) methods. The results of the excess thermodynamic functions and computer simulations indicate that the eutectic is not a mechanical mixture. IR spectroscopic and XRD studies confirm that there is some interaction between the components during the formation of the eutectic mixture. Moreover, the microstructure of the eutectic mixture at a molar ratio of 3:2 was more uniform than others, which was proved by DFT calculations. The Jackson's roughness parameter was found to be greater than 2, suggesting a faceted, irregular morphology. These results could pave a way for further investigation of the energetic eutectic system aiming to supersede TNT.