The title compound, C(10)H(12)FN(3)S, crystallizes in the same space group (P2(1)/c) as two polymorphic forms of 4-phenyl-1-(propan-2-yl-idene)thio-semicarbazone [Jian et al. (2005). Acta Cryst. E61, o653-o654; Venkatraman et al. (2005). Acta Cryst. E61, o3914-o3916]. The arrangement of mol-ecules relative to the twofold screw axes is similar to that in the crystal structure of the lower density polymorph. In the solid state, the mol-ecular conformation is stabilized by an intra-molecular N-H⋯N hydrogen bond. The mol-ecules form centrosymmetric R(2) (2)(8) dimers in the crystal through pairs of N-H⋯S hydrogen bonds.