The excess molar enthalpies H-m(E) of nitrous oxide (N2O)/hexane mixtures were measured in the liquid and supercritical region covering the whole concentration range. The H-m(E) values at 308.15 K and 7.64 and 9.48 MPa and at 318.15 K and 12.27 and 15.00 MPa are moderately positive in the hexane-rich region and moderately negative in the N2O-rich region. The H-m(E) values at 308.15 K and 12.27 and 15.00 MPa are moderately positive over the entire composition range. Large negative H-m(E) values are obtained at 318.15 K and 7.64 and 9.48 MPa. The changes observed in H-m(E) with temperature and pressure are discussed in terms of liquid-vapor equilibrium and critical constants for N2O/hexane. The H-m(E) values for N2O/hexane mixtures are also calculated using cubic equations of state (EOS) and the classical and Wong-Sandler mixing rules.