The mechanical properties of flax and jute woven fabrics were investigated and compared with each other. Mechanical properties of the yarns and fabrics were characterised and compared for each scale. The fabric structure, yarn physical properties, fibre cross-section, and fibre molecular structure parameters of the fabric were investigated. FTIR and TGA thermogram analyses were applied to the fabrics to characterise them. The fabric tensile strength was attributed to the composite tensile strength, but there was not a direct relation. The tensile strength of natural fibre fabrics was determined as significantly reduced depending on the temperature increase. This condition should be considered as an important limitation for composite applications.