The immiscible blend of poly(styrene-co-acrylonitrile) with an acrylonitrile content of 25 wt%, SAN25, and polycarbonate, PC, in the ratio 75/25 has been studied with respect to additives of poly(Ε-caprolactone), PCL. The PCL was found to compatibilize the blend, i.e., increased the impact strength, but a single phase ternary blend was not obtained even with 25 phr of PCL. PCL is completely miscible with SAN25 and with PC but was found to predominantly concentrate in the PC rich phase in the ternary blend.