We have successfully developed a novel biocatalytic strategy for the synthesis of chiral γ-thioether ketones. Depending on the choice of ERED, both enantiomers may be accessed with moderate to excellent ee. Mechanistic experiments showed a clear acceleration and the rate-determining SET in the presence of the vinyl sulfide co-substrate, suggesting a gating mechanism which enable the highly selective C-C bond formation. Indeed, in the absence of the co-substrate, the enzyme becomes inactivated with the FMN cofactor remaining in an oxidized state, which protein mass spectrometry suggests is due to unspecified modifications of protein by generated radicals. Finally, we demonstrated the synthetic applicability of the reaction on a 100 mg scale. We anticipate this reaction to be immediately useful in the development of compound libraries, for example during drug discovery, whereas applications on process scale require enzyme engineering and optimization of product isolation.