Recently, plant-based materials have gained significant attention in construction and renovation projects due to their eco-friendly nature, superior thermal insulation properties, and humidity regulation capabilities. However, accurately predicting the hygrothermal behavior of these materials in various environmental conditions can be challenging due to their hygroscopic and anisotropic nature. The difficulty in implementing hygrothermal transfer models lies in the lack of knowledge of the intrinsic characteristics of the plant materials. The objective of this paper is to provide an up-to-date review of the hygrothermal characteristics of plant materials to efficiently implement them in simulation tools. The review begins by discussing the characteristics of raw plant fibers and aggregates and then moves on to their characteristics at the composite material scale.