A novel molecularly imprinted polymer (MIP) electrochemiluminescence (MIP-ECL) sensor was developed for the highly sensitive and selective determination of ultra-trace levels of Ni²⁺. The complex Ni²⁺-dimethylglyoxime (Ni-DMG) was chosen as the template molecule to construct the MIP and then acted as a mimetic enzyme to catalyse the oxidisation of luminol to enhance the ECL signal. When the imprinted cavities were occupied by Ni-DMG in the rebinding process, the ECL intensities produced by the luminol-H₂O₂ ECL system on the MIP-modified electrode surface increased with increased concentration of the Ni-DMG complex. The highly sensitive determination of Ni²⁺ was achieved through a catalytic reaction. This technique could be used for the quantitative analysis of Ni²⁺ with concentrations from 3.0 × 10⁻¹² mol L⁻¹ to 6.0 × 10⁻⁹ mol L⁻¹. The detection limit was 1.01 × 10⁻¹² mol L⁻¹, which is much lower than that reported previously. In addition, the allowable amounts of interference ions in the MIP-ECL sensor were higher than that in other common molecularly imprinted sensors because of its excellent recognition of 3D cavity-to-complex molecules and ligand-to-metal ions. This method was successfully used to determine Ni²⁺ in real samples, such as apples, carrots and grapes, and has been proven feasible for practical applications.