Background: The connective tissue is a major tissue component in various body organs. Under certain conditions, the physiological regeneration of serious injuries in such tissues might fail to restore the original structure and function. The aim of this study was to investigate the effect of the enrichment of engineered connective tissues (ECT) with multiwall carbon nanotubes complexed with chitosan (C-MWCNT) on the physical properties of these tissues. Materials and methods: collagen-based ECT were generated by using human foreskin fibroblasts (HFF) or human ventricular cardiac fibroblasts (HVCF). The ECTs were enriched with 0.025%, 0.05% and 0.1% of C-MWCNT, and their rheological properties were investigated in addition to macroscopic and microscopic examination. Results: 0.1% C-MWCNT reduced the percentage of tissue shortening in both kinds of ECT. In HFF-based ECT 0.1% C-MWCNT significantly increased Young's module, the maximum stress, the breaking stress, the breaking strain and the yield point-stress. The 0.05% C-MWCNT significantly reduced the breaking strain and the yield point-strain, the later was also reduced by the 0.025% C-MWCNT. This appeared to be associated with an increase in stress fiber formation by HFF. In HVCF-based ECT, 0.025% C-MWCNT significantly increased the maximum stress, the breaking stress and the yield point-stress. However, this concentration had no effect on the Young’ module, which was even reduced by the 0.05% and the 0.1% C-MWCNT. The 0.1% C-MWCNT significantly increased the breaking strain and the yield point-strain. Conclusion: The effect of C-MWCNT on the physical properties of ECT might be dependent on the concentration of C-MWCNT and the type of the fibroblasts in the matrix. Generally in HFF-based ECT, C-MWCNT might increase the stiffness, strength and ductility of ECT, while in HVCF-based ECT C-MWCNT could increase their elasticity, strength and ductility.