In this work, the effect of the selective extraction of flax fibre components on the properties of flax woven fabric / epoxy biocomposites is investigated. Six treatments were applied to flax woven fabrics and their influence on fabric characteristics and the consequences on the fibre/matrix interface were studied. Components removal was evaluated by chemical composition and FT-IR analysis. Mechanical tests and SEM observations were used to study the composite interface. A defibrillation phenomenon within the fibre bundles with the extraction of some specific components was responsible for a significant decrease of the transverse strength of the biocomposites whereas the porosity was reduced for all the treatments used. Our results highlight the key role of cell wall components on the morphology and properties of flax woven fabric / epoxy biocomposites.