New classes of sustainable cementitious materials are needed to improve the environmental impact of cement-based building materials. This study describes the recent work carried out on cementitious materials made with various straw-fibre based additions. The straw was used as unprocessed and chemically processed. The chemical processing enabled fibre extraction down to the micro and nano scale. The different fibres, before and after processing, as well as the fibre-hydrated cement paste composites were characterized and the mechanical properties of the different materials were determined.