Potential energy surfaces fur the unimolecular decomposition reactions of HXGe=S (X = H, F, Cl, and Br) have been explored using B3LYP and CCSD(T) calculations. Five different reaction mechanisms are proposed: (A) 1,1-HX elimination, (B) 1,2-H shift, (C) 1,2-X shift, (D) H and XGeS radical formation, and (E) X and HGeS radical formation. According to our theoretical investigations, as in the case of HXGe=O, HXGe=S is found to be kinetically stable with respect to the unimolecular destruction reactions, despite its thermodynamic instability. Furthermore, the stabilization energies, which indicate the extent to which halogen substitution stabilizes the Ge=S double bond, increase along the series X = F, Cl, Br, and H and show a reasonable linear correlation with the electronegativity of the halogen.