In this work, the solid liquid phase equilibrium of N,N'-diethylthiourea (DETU) was investigated in different solvent systems from both solid-state structure and solution thermodynamics. The single-crystal structure of DETU was determined for the first time, and the intermolecular hydrogen bonding N-H center dot center dot center dot S interactions are dominant in the crystal packing. The thermodynamic equilibrium solubility was determined by the gravimetric method in 12 solvents (methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butyl alcohol, n-pentanol, acetone, butanone, methyl acetate, ethyl acetate, and acetonitrile) from 283.15 to 323.15 K. It was found that the solubility in alcohols decreases with increasing the length of the carbon chain and follows the rule of "like dissolves like", whereas in non-alcohol solvents, the rule does not apply. The experimental data were further correlated by the modified Apelblat equation, 2h equation, and NRTL model. All the correlation derivations are lower than 5%, and the NRTL model receives the best fitting performance. Furthermore, the thermodynamic functions of mixing including enthalpy, entropy, and Gibbs energy were derived, and the results expectedly suggest a spontaneous and entropy-driven mixing process. All the crystallographic and thermodynamic data reported in this study will provide the fundamental data for designing and optimizing the crystallization of DETU.