The durability of concrete structures is strongly affected by the ease of water and ion penetration. Polymeric surface treatment with epoxy and silane are commonly used to provide a barrier to the ingress of water and ions. In this investigation, the improvement of barrier properties of epoxy and silane by the incorporation of nano-sized organoclay was studied. The water vapor transmission test and the salt spray resistance test were conducted to evaluate the resistance to moisture and chloride penetration respectively. The test results indicate significant improvement in moisture penetration resistance when small amounts of organoclay, ranging from 1 wt% to 5 wt%, are introduced into neat epoxy and neat silane. Polymer/organoclay nanocomposites are also more effective than neat polymers in inhibiting the ingress of chloride ion into the concrete, with 3 wt% epoxy/organoclay nanocomposites showing the best performance. The results demonstrate the potential application of polymer/organoclay nanocomposites as surface treatment material for concrete structures.