The thermodynamic aspects of the dissolution of water (moisture) in diesel fuels have been considered. For theoretical analysis, the basic features of moisture dissolution in individual liquid hydrocarbons and diesel fuel at different temperatures have been considered. The parametric equations proposed in this work made it possible to determine the heats and entropies of a solution of water in individual liquid hydrocarbons and diesel fuel. The values obtained for diesel fuel were about 40 kJ/mol and 92.08 J/(mol K), respectively, which correspond to the chemical composition of the test diesel sample. On the basis of the results of the study, a mechanism has been put forth for the interaction of water molecules with the molecules of individual hydrocarbons and diesel fuel.