The investigation on electrochemiluminescence (ECL) multiplexing bioassays mainly focuses on simultaneously detecting either proteins or nucleic acids. To overcome the limitation of a short waveband for spectrum-resolved ECL multiplexing bioassays, herein, a highly monochromatic (FWHM <40 nm) and bandgap-engineered ECL luminophore, that is, mercaptopropionic acid-capped and Zn2+-mediated aggregation-induced emission (AIE) assembly of Au nanocrystals (NCs) (Zn2+-AIE-AuNCs), of strong emission and the maximum emission wavelength at 485 nm is developed. The highly monochromatic and bandgap-engineered ECL (485 nm) of Zn2+-AIE-AuNCs can multiplex with the single-waveband and surface-defect-involved ECL (775 nm) of dual-stabilizer-capped CuInS2@ZnS NCs (CIS@ZnS-NCs), enabling a spectrum-resolved ECL multiplexing strategy with different NCs luminophores of a similar particle size as tags. This ECL multiplexing strategy can be utilized to simultaneously detect antigen and DNA probe together without any additional signal amplification procedure and obvious spectroscopic cross-talk, in which the highly monochromatic ECL from Zn2+-AIE-AuNCs is utilized to dynamically determine human carcinoembryonic antigen from 1 pg/mL to 50 ng/mL with a limit of detection (LOD) of 0.3 pg/mL, while the single-waveband ECL from CIS@ZnS-NCs is employed to linearly detect wild-type p53 from 1 pM to 50 nM with a LOD of 0.5 pM. The ECL immunoassay of the proposed strategy is free from the interference of the synchronously conducted DNA probe assay and vice versa, which would open an avenue to couple the immunoassay and DNA probe assay together for clinical colon and breast cancer identification.