In the context of reducing the environmental footprint, the composite materials industry is in pursuit of replacing, partially or totally, the synthetic raw materials with renewable sustainable ones. In recent years, success has proven to come from using vegetable fibres for reinforcement. In Western Europe, multiple enterprises took part in the commercialisation of vegetable fibres destined for composite materials, and this opportunity has arisen from the reduced demand in the habitual textile industry. In Romania, such a sector is not established, even though a similar development potential exists due to the reduced demand of fibres for textiles during the last 30 years and the appropriate climate conditions for cultivation. Therefore, it is worth looking at the reasons behind this absence, and investigating the current economic context can allow for competitive prices. This study followed this line of investigation by analyzing the mechanical properties. Two types of fibres were investigated, hemp and flax, cultivated in Romania. The literature shows them as being the most prominent for composite reinforcement and both have a long history of cultivation on the Romanian territory. Tensile tests were used for this reason, and the tensile stress--strain curves revealed the Young modulus and strength at failure for the two types of fibres. Samples of several lengths were analysed, as it has been noted to be an important factor of influence. Due to the high dispersion of experimental results, characteristic to reinforcement fibres, a statistical approach was used. Several types of stress--strain curves were determined, with bi-linear or tri-linear evolutions, all in the limits of what is available in the literature regarding the two types of fibres.