Carbon nanotubes and magnetite nanoparticles are materials with unique and extraordinary properties having a wider range of applications in diverse areas of science and engineering. In addition, this kind of nanomaterial can be linked to a polymeric matrix resulting in a multifunctional composite material with enhanced properties. We present here the synthesis of chitosan-starch (CH-S) films reinforced with magnetite decorated carbon nanotubes and their properties were studied. In order to synthesize the nanocomposite material, multi-walled carbon nanotubes (MWCNTs) were first decorated with magnetite nanoparticles (MNPs) of 13.4 ± 3.7 nm using MWCNT/MNPs ratios of 0.2 and 2. Chitosan chains were used as bonding agent, and in the next step, MWCNT/MNPs was incorporated into a polymeric matrix of 70% of chitosan and 30% of starch. Concentrations of magnetite decorated MWCNT in the films were 0.1%, 0.25%, and 0.5%, respectively. Thermogravimetric and dynamic mechanical analyses were performed. The lowest concentration polymeric film showed homogeneous particle distribution, and this homogeneity was lost due to the formation of large agglomerates (≈192 nm) at higher concentration. This behavior affected the physical properties of nanocomposites. Storage modulus of the film decreased as the concentration of decorated MWCNT increased indicating dependence of storage modulus on agglomerates size. The storage modulus increased in the temperature range of 150°-250°C. This behavior was more pronounced at 1:3 ratios of MWCNT/MNPs due to the stronger interfacial adhesion between nanoparticles and the polymeric matrix. The magnetic behavior and electrical conductivity of the nanocomposites were also studied.