Copper is one of the essential trace elements in human body which plays a vital role in the processes of fundamental physiology. Therefore, analysis and detection of copper ions has attracted tremendous attention. In this paper, an electrochemical sensor was successfully developed based on 5-sulfosalicylic acid modified nanocomposite of molybdenum disulfide nanosheets and oxidized mull-walled carbon nanotubes (SSA/MoS2/o-MWCNTs). The nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy, element mapping, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and electrochemical measurements. Then, nanocomposite-modified glassy carbon electrode was used for the detection of Cu2+. Electrochemical analysis of Cu2+ was performed by differential pulse voltammetry, and the effects of pH, deposition potential, and deposition time were investigated. The results showed that the peak current increased linearly with increasing Cu2+ concentration over the range of 0.1-11 mu M and a detection limit of 0.057 mu M (S/N = 3). Finally, the developed sensor was applied for the analysis of Cu2+ in lake water and dairy products, and the results were consistent with the results of ICP-MS analysis. Therefore, this work demonstrates that the proposed electrochemical sensor can be easily used for the daily monitoring of Cu2+.