This study reports the experimental investigation of a commercial formulated lime binder (Tadical PF70) modification effect on the durability of hemp concrete specimens when subjected to continuous wetting and drying cycles. The influence of partial replacement of Tradical PF70 binder by metakaolin has been studied by testing the physico-mechanical properties of samples including mass loss, porosity, compressive and flexural strengths, and corresponding toughness for aging conditions of 15, 25, and 50 wetting/drying cycles. Considered as a critical factor which contributes to the specimen deterioration, a separate investigation of the degradation rate of the embedded hemp particles in specimens at aging cycle intervals has been also performed. The results have shown that the pozzolanic reaction of amorphous silica contained in metakaolin with dissolved calcium hydroxide appears to significantly minimise the degradation of hemp concrete. The corresponding reaction consumes calcium hydroxide to produce hydrated calcium silicates and in turn will lead to the lowest alkalinity of pore solution which is considered as the main responsible for hydrolysis of hemp particles. The examination of the relationship between embedded hemp particle deterioration degree and the loss of mechanical properties of hemp concrete has shown that the use of metakaolin is an effective means to improve durability of specimens mainly through the restraint of hemp particle degradation.