Supercritical CO2 is a promising solvent for application in polymer blending and foaming. Interfacial tension is a key parameter in determining the bubble nucleation and growth rates, as well as droplet breakup in blending. However, very limited data are available in the literature for CO2-polymer systems. In this work, pendant drops were imaged in a high-pressure, high-temperature view cell for determining the interfacial tension between polystyrene (PS) and CO2 (210-230 degreesC and pressure up to 140 atm), and between polystyrene and two different molecular weight polypropylenes (PP) (both saturated with CO2 at 220 degreesC and pressures up to 165 atm). The interfacial tensions in polymer/CO2 and polymer/polymer systems decrease significantly with increasing CO2 pressure and then level off at higher CO2 pressures. Density gradient theory combined with an equation of state was applied in predicting the interfacial tension between PS and CO2 starting from only the surface tension data of pure PS at the temperature of interest. The theory captures well the magnitude of the depression at high pressure, however, it severely underpredicts the interfacial tension in the low pressure region below 60 atm.