The pressure dependence of interfacial tension between methane and octane at five temperatures has been determined using the pendant-drop method. The experimental results show that the interfacial tension value decreases with the increased temperature and pressure. The higher temperature and pressure has a positive contribution on weakening the intermolecular interaction between methane and octane. The surface excess concentration for methane on octane at different temperatures and pressures and the surface free energies of adsorption for (methane + octane) were calculated and compared with the (methane + water) system. The calculated results show that methane is more preferred for the adsorption on octane than on water.