Abstract This study evaluated the effect of multi‐walled carbon nanotubes (MWCNT) addition on the thermomechanical, and electrical responses of unidirectional flax fibers/Elium acrylic modified carbon nanotubes‐based composite. The manufacturing process of these laminated composites involved infusing the nanofillers onto the fibers, ensuring good dispersion of MWCNT within the matrix. Regardless of the rate of incorporated nanotubes, this study revealed a significant deterioration of the mechanical properties in tension and viscoelastic properties of the Elium acrylic resin‐based nanocomposite. The electrical conductivity significantly increased for all nanocomposites and laminated composites. In contrast to the nanocomposite, the unidirectional flax fibers/MWCNT/Elium acrylic composite exhibited a considerable improvement in mechanical properties. An increase in Young's modulus and stress at break of about 27% and 23% respectively, was achieved for the material loaded with 2 wt% of MWCNT. The presence of MWCNT reduces the saturation weight by 5% for the unidirectional composite filled with an amount of 1.5 wt% in MWCNT. Highlights Improving the electrical properties of nanocomposites and unidirectional fibers (UD) composites. Improving the mechanical properties of Elium/flax/multi‐walled carbon nanotubes (MWCNT) composites. Influence of MWCNTs on the water absorption of UD composites. Influence of MWCNT on the glass transition temperature of nanocomposites. Inhibiting polymerization of MWCNT with Elium.