Despite its importance, the description of liquid–liquid extraction is made difficult because the link between the experimental methods and the interactions present in the solution is not direct due to the many organisation phenomena that can occur. We propose a new methodology combining microcalorimetric measurements and molecular modelling to better describe the nature and strength of these interactions in these complex fluids by focusing on extractant-diluent mixtures (N,N-dialkylamides + n-alkanes). Enthalpies of dilution were obtained by microcalorimetric measurements at 298 K for each n-dodecane and n-heptane with DEHiBA and for n-dodecane with DEHBA. These results have been compared, thanks to a new method that we present here, to molecular dynamics simulations carried out on these same systems. We especially analyzed the influence of the alkyl branching of the extracting molecules and the role of the diluent. Globally, the excess enthalpy is such that these mixtures are energetically not very different from regular solutions but the detailed balance shows an important attraction between the extractants, which can lead to the formation of macromolecular entities favouring extraction. Calorimetry appears to be a method of choice for linking experiments and molecular modelling in these complex liquid mixtures, and experimental developments could benefit from using it more often, especially to validate force-fields.