This work is focused on the field of gas sensor for sensing the toxic gases which is highly harmful to environment. The semiconductor metal oxide nanoparticles of manganese ferrites and copper doped manganese ferrite (MnFe2O4 and Cu: MnFe2O4) was successfully developed. The characterization like crystal structure, surface morphology, optical bandgap, elemental composition and functional group analysis for the developed materials were carried out using X-ray Diffraction (XRD), Scanning electron microscope (SEM), Diffused reflectance spectroscopy (DRS), Energy dispersive X-Ray analysis (EDAX) and Fourier Transform (FT-IR) studies respectively. The ammonia gas (NH3) was taken as test gas and the sensitivity of prepared samples were analyzed with different ppm (200–400) of gas molecules at room temperature. The sensing percentage gradually improved with the increase in Cu2+ concentration also with the increase in ppm of the gas. However, the recovery time of the material is increased with increase in the ppm.