We report on the destabilization of the 6H-SrIrO₃ polymorph through partial substitutions of zinc and lithium for iridium to form perovskites. The perovskites crystallize in the orthorhombic space group Pbnm: SrIr_1−xZn_xO₃ is found for 0.25 ≤ x ≤ 0.33, while SrIr_1−xLi_xO₃ is found only for x = 0.25. The Zn and Li ions are randomly distributed in the B-site lattice. Analysis shows that the perovskite stabilization is not driven by changes in average ionic size but rather is due to destabilization of the face-sharing octahedra that are present in 6H-type SrIrO₃. Magnetic susceptibility measurements show Curie–Weiss behavior, with relatively large temperature independent contributions, and that the iridium atoms have low effective moments, 0.52 to 1.08 μ_B per Ir. The resistivity of SrIr_0.67Zn_0.33O₃, characterized by Mott variable range hopping type semiconducting behavior, indicates that substituted Zn ions introduce significant disorder into the system. SrIr_0.75Li_0.25O₃ has a significant linear contribution to the specific heat at low temperatures.