Guided by a superb dual-ions cosubstitution strategy, two novel, highly optically anisotropic hybrid bismuth halides are designed and synthesized. The first compound, Gu₃Bi₂NO₃Cl₈ (Gu = C(NH₂)₃), is developed using the 2D perovskite halide Cs₃Bi₂Cl₉ as the maternal structure. This involved substituting all Cs⁺ cations with organic Gu⁺ and replacing some Cl⁻ anions with [NO₃]⁻. Further substitution of Cl⁻ with additional [NO₃]⁻ resulted in the formation of nitrate-rich Gu₂Bi(NO₃)₃Cl₂ crystal, exhibiting a 3.4-fold increase in [NO₃]⁻ per unit volume. Both compounds have a structurally 0D nature, comprising bismuth-centered polyhedra formed by coordinated chlorides and monodentate/bidentate nitrate moieties, with Gu⁺ serving as a separator and linker. Notably, the presence of superb optically anisotropic dual-ions, i.e., planar Gu⁺ and [NO₃]⁻, enables these crystals to possess sharply enhanced optical anisotropy, with birefringence values more than 1 order of magnitude higher than that of the initial crystal Cs₃Bi₂Cl₉ (0.162/0.186vs 0.011 at 546 nm). The discovery and characterization of Gu₃Bi₂NO₃Cl₈ and Gu₂Bi(NO₃)₃Cl₂ crystals provide new insights into achieving expected modifications in optical properties through the utilization of a dual-ions cosubstitution strategy.