Previous studies show that both metakaolin (MK) and polymer can respectively improve certain mechanical and durability properties of concrete. Also, recent studies show that a combination of MK and polymer further enhances the mechanical properties by complement of each other. However, the knowledge of the effect on durability, a critical governing factor of concrete for the applications in extreme environments such as sewage, off-shore and bridge structures, has not been well established yet. This paper reports on a comprehensive study of the effect of metakaolin as a supplementary cementitious material together with polymer as admixture on the durability of concrete at relatively old ages. The results confirm that replacing Portland cement with 15% metakaolin and an additional 5% polymer (by weight) provide the optimum improvement for Portland cement concrete on both mechanical properties and durability. (C) 2018 Elsevier Ltd. All rights reserved.