[(2-{[6-(1,3-Benzothiazol-2-yl)pyridin-2-yl]carbonylazanidyl}phenyl)sulfanido]nickel(II), [Ni(C₁₉H₁₁N₃OS₂)], crystallizes in the centrosymmetric monoclinic space group P2₁/n with one molecule in the asymmetric unit. The expected ligand, a bis-Schiff base derived from pyridine-2,6-dicarbaldehyde and 2-aminothiophenol, had modified in situ in a both unexpected and unsymmetrical fashion. One arm had cyclized to form a benzo[d]thiazol-2-yl functionality, while the imine linkage of the second arm had oxidized to an amide group. The geometry about the central Ni^II atom is distorted square-planar N₃S. The molecules form supramolecular face-to-face dimers via rather strong π–π stacking interactions, with these dimers then linked into chains via pairwise C—H...O interactions.