Thin films of tin monosulfide were chemically deposited on GaAs substrates and on GaAs with intermediate PbS layers. GaAs surface treatments with alkaline solutions containing Pb2+were shown to facilitate the formation of π-SnS, a new cubic polymorph in the tin monosulfide system. Compactness and phase purity of the films were further improved when depositing onto a chemically deposited PbS intermediate layer, resulting in epitaxial orientation relations between the layers. Deposition onto GaAs(111) resulted in (111)[01̄1]PbS‖(111)[01̄1]π-SnS, while deposition onto GaAs(100) resulted in (110)PbS‖(110)π-SnS. Polarized Raman measurements demonstrated inherent anisotropy, as expected for epitaxial films.