In the furniture, automotive and contruction industries, there is increased demand for cost-effective and lightweight biocomposites. The objective of this work was to develop new natural fibre-based composites with specific properties. Palm and pineapple leaf fibres were chosen in association with polypropylene (PP). The first step was to investigate the effect of these natural fibres as reinforcement for PP. The evolution of chemical structure and crystallinity was proposed with infrared spectroscopy measurements and differential scanning calorimetry thermograms, respectively. The assessments of mechanical properties with tensile tests and melt viscoelastic behaviour were also investigated. The study enabled to distinguish the influence of fibre content. The second step in our work was to assess the composite durability after ultraviolet exposure or thermal ageing. The oxidation level was calculated. The long-term evolution of thermal and mechanical properties was also proposed. As a result, the PP/pineapple leaf composite revealed a promising biocomposite.