In the title compound, C12H15N3O2S, the 1,3-benzdioxole fragment is nearly planar [the maximum deviation being 0.0515 (14) Å], the N-N-C(=S)-N fragment is also nearly planar [the maximum deviation being 0.0480 (10) Å], and the dihedral angle between their mean planes is 23.49 (10)°. In the crystal, mol-ecules are linked by pairs of N-H⋯S hydrogen bonds, forming inversion dimers. The dimers are stacked along the a axis with neighbouring columns having the same direction; however, the mol-ecules show different orientations leading to a centrosymmetric arrangement. In the crystal, the methyl-ene group of the ethyl substituent and the terminal methyl H atoms are disordered over two sets of sites and were refined using a split model with an occupancy ratio of 0.5:0.5.