This paper aims at assessing the experimental and analytical parameters of moisture diffusion of quasi-unidirectional and twill flax-fibres reinforced epoxy composites. The tested specimens of these composites were elaborated by hand lay-up technique at room temperature by using a vacuum moulding process. For several days, the samples were subjected to three ageing conditions, in order to evaluate the percentage of moisture uptake according to the ageing time. Next, the collected experimental data were analysed by using an optimisation program of Matlab software in order to identify the 3D diffusion parameters. The obtained results showed that the morphology and the anisotropy of flax fibres had a significant influence on the moisture diffusion. It also showed that moisture diffusion behaviour predicted by the 3D Fick model was in good agreement with the experimental results.