Cottonisation of flax not only makes flax usable for producing textiles, it also further divides the technical fibre into (bundles of) elementary fibres and removes partly the alkali-sensitive pectin and hemicellulose. An experimental investigation was performed to assess the characteristics of cottonised flax in fibre reinforced cementitious composites. The fibre and composite properties are compared with technical flax and PVA fibres. Strength/strain curves of the fibres and composites are compared to evaluate the mechanical performance. Not only tensile strength and stiffness but also first crack strength and peak stress, work of fracture as a measure for multiple cracking and the visual closure of individual cracks by self healing are analysed. Cottonisation of flax enhances modulus of elasticity, peak stress and strength at first crack of concrete, in comparison to technical flax fibres.