Although the electrochemiluminescence (ECL) of metal nanoclusters has been reported, revealing the correlation between structure and ECL at an atomic level is highly challenging. Here, we reported the impact of the metal core of Au20(SAdm)12(CHT)4(Au20-AC for short; SAdm = 1-adamantanethiolate; CHT= cyclohexanethiol) and its isomer Au20(TBBT)16(TBBT = 4-tert-butylthiophenol) on their solution-state and solid-state electrochemiluminescence. In self-annihilation ECL experiments, Au20-AC showed a strong cathodic ECL but a weak anodic ECL, while the ECL signal of Au20(TBBT)16was weak and barely detectable. Density functional theory (DFT) calculations showed that the Au7kernel of [Au20-AC]-is metastable, weakening its anodic ECL. Au20-AC in solution-state displayed an intense co-reactant ECL in the near-infrared region, which is 7 times higher than that of standard Ru(bpy)32+. The strongest solid-state ECL emissions of Au20-AC and Au20(TBBT)16were at 860 and 770 nm, respectively — 15 nm red-shifted for Au20-AC and 20 nm blue-shifted for Au20(TBBT)16, compared to their corresponding solid-state photoluminescence (PL) emissions. This work shows that ECL is significantly affected by the subtle differences of the metal core, and offers a potential basis for sensing and immunoassay platforms based on atomically precise emissive metal nanoclusters.