Enthalpies of mixing of R- and S-limonene in non-polar solvents in the entire range of mole fractions were measured at 298.15 K. The enthalpies of mixing were negative for all concentrations in dilute concentration, but increased by increasing the concentration of limonenes in solutions. Ultimately positive excess enthalpies were shown in high concentration. Enthalpies of mixing were compared with theoretical estimation by COSMO-RS.