Flax fibers have been observed to have specific mechanical properties on par with E-Glass. However, lack of knowledge on their mechanical behaviour as well as the absence of practical modeling tools have impeded the flax fiber from being used in structural applications. In this thesis, compressive mechanical testing was performed Flax/Epoxy laminates in order to capture and quantify the flax composite’s non-linear behaviour with emphasis on damage and plasticity evolutions. A continuum damage mechanics-based on the standard Mesoscale Damage Theory (MDM) developed previously by Ladeveze and LeDantec was developed to include compressive damage and plasticity evolutions. The model parameters were derived from experimental data and optimized using open-source algorithms. Validations have been performed on Flax/Epoxy and EGlass/Polyester laminate composites in compression, as well as E-glass/Epoxy in tension. The model successfully predicts the composite’s mechanical behaviour, and offers a robust predictive tool capable of aiding engineers and designers in the development of load-bearing natural fiber composites.