The title compound, C12H9BrN2OS2, was obtained by reacting 6-bromo-benzo[d]thia-zole-2-carbo-nitrile in iso-propanol with ethyl 2-mercapto-2-methyl-propano-ate at reflux temperature for several hours. The resulting di-methyl-oxyluciferin derivative shows partial double-bond character of the carbon-carbon bond between the two heterocyclic moieties [C-C = 1.461 (3) Å]. This double bond restricts rotation around this C-C axis, therefore leading to an almost planar mol-ecular structure [N-C-C-S torsion angle = 9.7 (3)°]. The five-membered thiazoline ring is not completely planar as a result of the bulky S atom [C-S-C-C torsion angle = 5.17 (12)°].