The reaction of NiII acetate tetrahydrate with 4-methyl-2-(1,2,3,4-tetrahydronaphthalen-1-ylidene)hydrazinecarbothioamide in a 2:1 molar ratio and recrystallization from dimethylformamide yielded the title compound, [Ni(C12H14N3S)2]·C3H7NO. The ligands act as monoanionic κ2N1,S-donors, forming five-membered metallarings. The NiII ion is fourfold coordinated in a distorted square-planar cis-configuration, which is rather uncommon for monothiosemicarbazone complexes. Intramolecular H...Ni trans-interactions are observed [H...Ni distances are 2.50 and 2.57 Å] and thus anagostic interactions can be suggested. The Hirshfeld surface analysis indicates that the major contributions for the crystal packing are H...H (66.6%), H...S (12.3%) and H...C (10.9%) interactions. In the crystal, the complex molecules are linked by dimethylformamide solvent molecules through N—H...O interactions into one-dimensional hydrogen-bonded polymers along [010].