Flax has been usually used to produce natural cellulose fibres with properties suitable for composite, textile, and other high-value fibrous applications. Spanish Broom, extracted by a physical-chemical process, is a source of cellulose fibres that can be used, as well as flax, in various fields (textile, paper, composites etc.). The aim of this study was to describe the chemical composition, morphology and tensile properties of Spanish Broom fibres in comparison with flax. The morphology of both fibres was established by optical microscopy (OM). The chemical composition and tensile properties of Spanish Broom fibres were determined according to conventional methods. The results show that Spanish Broom fibres have a higher cellulose content (91.7%) and better tensile properties than flax fibres. Moreover, Spanish Broom fibres have a smaller diameter (7-10 μm) than flax (17-24 μm), as observed by OM, and the cross-sections show an irregular polygonal shape with well defined lumen. Spanish Broom fibres were found to have very good tensile properties as well as thermal stability and could successfully replace flax in many applications.