In this study we report the green synthesis of nontoxic and stable Cu nanoparticles (NP) using chitosan/starch hydrogel with reducing/capping ability without using any harsh reducing agents. Starch was used as a reducing agent for the synthesis of Cu NPs that was further stabilized by chitosan polymers. The in situ prepared Cu NPs/CS-Starch bio-composite were characterized by advanced physicochemical techniques like Fourier Transformed Infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDX), X-ray Diffraction (XRD), UV–Vis, TGA and Inductively Coupled Plasma-Optical Emission Spectroscopic (ICP-OES) study. It has been established that Cu NPs/CS-Starch bio-composite have a spherical shape with a mean diameter from 5 to 7 nm. Cell viability of Cu NPs/CS-Starch bio-composite was very low against common human thyroid carcinoma cell lines i.e. TPC1, BCPAP and FTC133 without any cytotoxicity on normal cell line. The best anti-human thyroid carcinoma effects of Cu NPs/CS-Starch bio-composite was observed against the TPC1 cell line. For investigating the antioxidant properties of Cu NPs/CS-Starch bio-composite, the DPPH assay was used in the presence of butylated hydroxytoluene as the positive control. Cu NPs/CS-Starch bio-composite inhibited half of the DPPH molecules in the concentration of 207 µg/mL. The antioxidant activity of Cu NPs/CS-Starch bio-composite is significantly related to its anti-human thyroid carcinoma potentials. Based on to the above findings, the Cu NPs/CS-Starch bio-composite could be administrated for the treatment of several types of human thyroid carcinoma in humans.