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The triple-layer Sr₄Ru₃O₁₀ is a spin-orbit-coupled metal featuring an intriguing combination of a ferromagnetic and a metamagnetic states. We report a comprehensive study of single-crystal neutron and x-ray diffraction on Sr₄Ru₃O₁₀ with 4% iridium doping. The system crystallizes in an orthorhombic Bbem structure in which two triple-layers are related by a base centering symmetry operation within one unit cell. The Ir doping at the Ru site sensitively alters the structural balance between the RuO₆ layers, as such the two outer-layer octahedra rotate about the c-axis in enhanced to 6.7◦, while the central-layer one rotates in the opposite direction by 11.0◦. The increased lattice distortion stabilizes a collinear ferromagnetic state with magnetic moments fully aligned along the c-axis. The emerging perpendicular magnetic anisotropy naturally increases the critical field for the in-plane metamagnetic transition to 4.5 Tesla. All results highlight the critical linkage between the magnetic properties and underlying lattice through orbital degree of freedom and provides a viable route for an efficient manipulation of the magnetic states with novel functionalities.