Phase-pure polycrystalline Sn1−δS has been prepared using a one-step microwave-hydrothermal procedure. Its structural characterization by neutron powder diffraction and transmission electron microscopy shows an orthorhombic Pnma phase at room temperature with the presence of a significant amount of Sn vacancies (Sn0.87S), randomly located in the crystal structure. This work proves that this inexpensive 2D material, constituted by high abundance elements, is a promising candidate for thermoelectric applications. This is confirmed by its relatively high carrier density and good mobility (2.5 × 1018 cm−3 and 13 cm2 V−1 s−1 at room temperature, respectively) found in the microwave-hydrothermal-synthesized sample, which favours high thermoelectric performance. In addition, a remarkably high Seebeck coefficient (682 μV K−1) combined with low electrical resistivity (5.6 × 10−4 Ω m) and thermal conductivity (0.57 W m−1 K−1) at 523 K produces a reasonably high figure of merit ZT of 0.76.