Textile Reinforced Mortar (TRM) systems are widely recognized as effective solutions for the retrofitting of masonry structures, primarily due to their strong compatibility with existing materials and their reversible properties. In recent years, the use of vegetable-based natural textiles as reinforcement in TRM systems has gained increasing attention, offering a more sustainable and cost-effective alternative while still delivering satisfactory structural performance. Although studies initiated over the past decade have explored the short-term tensile characteristics of flax textiles, investigations into their long-term durability—crucial for structural applications—are still limited. Indeed, the overall performance of Natural TRM (NTRM) applications largely depends on the durability of the system over time, particularly in maintaining mechanical integrity when interacting with historical masonry substrates. This study focuses on evaluating the tensile behaviour of flax textiles, with particular emphasis on their residual performance after accelerated ageing. Both unaged and aged flax textiles were tested under uniaxial tension to assess their mechanical performance. The stress-strain response was captured using non-contact 2D Digital Image Correlation techniques to avoid altering the textile behaviour. The first results reveal that ageing has a significant detrimental effect on the flax textile reinforcement, leading to a considerable reduction in the tensile strength of the material.