The excess molar enthalpies (H-E) of the carbon dioxide + diisopropyl ether system were measured in the vicinity of the critical point of carbon dioxide using a flow-type isothermal microcalorimeter at temperatures from (298.15 to 308.15) K and pressures from (5.0 to 7.5) MPa. Mixtures showed strong exothermic behavior in these regions. The minimum negative value of H-E found in this study was about -7.8 kJ.mol(-1) at 298.15 K and 5.0 MPa. The experimental results were represented using a composition-dependent equation and the Peng-Robinson equation of state with van der Waals one fluid mixing rules.