► Four parameters influencing mechanical properties of hemp concretes are studied. ► The curing conditions can strongly affect the mechanical behavior of the material. ► The mechanical behavior of a hemp concrete is related to a large extent to its age. ► The binder content hugely influences the setting and hardening of the material. ► The use of small particles leads to reduce the setting process of hemp concrete. Hemp concrete is a multifunctional ecological material used in buildings. Due to its high porosity (about 80% in volume), it presents an “atypical” mechanical behavior and its thermal and acoustic properties are particularly interesting. It is today possible to design this material according to the required use. This paper focuses on the mechanical properties of hemp concrete. It is shown that extreme curing conditions (30%, 75% and 98% RH) are prejudicial to the mechanical setting of the hydraulic binders whereas only high relative humidity disrupts the one of the air lime-based binder. It is also established that the binder content hugely influences the setting and hardening of the material. Finally, according to the hemp particle size, it appears that small particles (about 3 mm in length) lead to reduce the porosity and consequently the setting process of hemp concrete as compared to concrete manufactured with large particles (about 9 mm).