In France, the use of flax fibers as reinforcement in composite materials is growing exponentially in the automotive sector, thanks to their good physicochemical properties, environmental reasons, health neutrality and due to the European Council Directives on the reuse, recycling and valorization of car components and materials. The aim of our study is to investigate biochemical, physicochemical, and mechanical properties of technical flax fibers to evaluate the impact of transformation processes (scutching, hackling, and homogenization) on final properties of associated composite materials. Different chemical analysis such as Van Soest (biochemical fraction measurement), FTIR (Fourier Transform InfraRed spectroscopy), and XRD (X-ray diffraction) were carried out on different process modalities and show that there is no significant difference in terms of biochemical fraction and crystallinity index. By the same token, mechanical behavior shows that Young's modulus is not affected by the transformation process. This result is also observed for thermal behavior. The results highlight the fact that the transformation processes of technical fibers do not really affect their physicochemical and mechanical performances.