Oscillation is an intriguing phenomenon in nature. However, structural oscillation has not yet been found in semiconducting nanoparticles, primarily due to the difficulty of structural resolution at the atomic level. The emergence of gold nanoclusters (ultrasmall nanoparticles) has provided an excellent opportunity to address some challenging issues in the nanoparticle field. Herein, two Au28(CHT)20 (CHT: cyclohexanethiolate) structural isomers (Au28i and Au28ii for short) were concurrently synthesized by employing a quasi-antigalvanic method, and they could be reversibly transformed into each other for at least 10 cycles, driven by dissolution and crystallization processes. The transformation from Au28ii to Au28i is solvent-dielectric-constant-dependent, with a notable deuteration effect from dichloromethane. The markedly different photoluminescence values of these two isomers not only have important implications for the structure–property correlations but also have potential applications in converting, sensing, etc.