Invisible mercury ion is an incredibly toxic pollutant to the atmosphere. Thus a quick and sensitive detection method is of considerable importance for toxicological assessment, environmental protection and human health. A novel electrochemical sensing system has been developed for the detection of mercury (Hg²⁺) ions in canned tuna fish and tap water. The sensing platform was developed on the cubic copper-metal-organic framework (Cu-MOF) based nanoparticles. Cu-MOF has a porous architecture with a large, unique surface area that is favorable for mercury ions adsorption and preconcentration. The electrochemical properties of Cu-MOF nanoparticles modified electrode were investigated. Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were applied for the detection of mercury in 0.1 M phosphate buffer (PB) at pH 9 under ambient conditions. Under optimized conditions, the limit of detection (LOD) for Hg²⁺ is around 0.0633 nM with a linear range of 0.1–50 nM. Cu-MOF nanoparticles were successfully applied to the analysis of mercury ions in canned tuna fish and tap water. The developed sensor demonstrated satisfactory anti-interference, reproducibility, reliability, repeatability and applicability for the detection of mercury ions. This proof of principle serves as a steppingstone towards promoting ultrasensitive and precise assay for the detection of mercury.