This paper describes the mechanical behavior of flexible polymer nanocomposite films loaded with MWCNT/Fe3O4 nanopowders as filler. A simple and expedite casting evaporation methodology was used for manufacturing the PVA-based films with a portion of HPC and PVDF polymers. The average crystallite size of superparamagnetic magnetite nanoparticles (NPs) deposited onto the functionalized carbon nanotubes (f-MWCNTs) was located between ca. 9.6–11.9 nm, while the analysis of VSM data came up with results showing an awful lot of magnetic strength for these treated nanopowders. A non-covalent functionalization procedure on the resultant colloidal MWCNT/Fe3O4 nanopowders was carried out by introducing hydrophilic PVA chains around the tubes. Importantly, the hypothesis behind our work was that the tight PVDF polymer could effectively enhance the tensile strength of soft PVA polymer film, whereas high-stretchable HPC polymer could be used to increase the elongation at break of PVA-based films. Advantageously, this idea therefore gave rise to interesting mechanical indices of PVA-based polymer films, and even as a significant observation it was found that the magnetic interactions between magnetite NPs could further amplify the mechanical stability of the specimens. We emphasize that the resultant MWCNT/Fe3O4-contained multi-polymer films are thus capable of being exploited in industrial and medical gadgets such as mechanical sensors, biohybrid swimmers, artificial hearts, mechanical respiration devices, and the like.