Mercury-based electrodes have been employed for the electrochemical determination trace level of heavy metals. However, due to the toxicity of mercury, mercury-free materials are encouraged to develop for on-site monitoring of heavy metals. In this work, N-doped carbon spheres/multi-walled carbon nanotubes (N-CSs/MWCNTs) hybrid materials were successfully fabricated with a low-cost convenient method. The synthesized N-CSs/MWCNTs composites were used to fabricate chemically modified electrode for selective and sensitive determination Cu(II) by differential pulse anodic stripping voltammetry (DPASV). Under the optimized experimental conditions, the proposed electrode displayed a good linear dynamic range of 0.5-200 mu g L-1 with a correlation coefficient of 0.99. Its limit of detection (LOD) was estimated to be 0.092 mu g L-1. Moreover, the repeatability, reproducibility, and stability of the modified electrode were also explored. Finally, the proposed electrode can be applied to quantify Cu(II) content in lake water and human saliva samples.