Interfacial magnetism in complex oxide heterostructures underlies both fundamental many-body physics and advanced spintronic applications. Here we report a pronounced stacking-order dependence of magnetic coupling in $\text{L}{\text{a}}_{0.78}\text{C}{\text{a}}_{0.22}\text{Mn}{\text{O}}_3/\mathrm{SrRu}{\mathrm{O}}_3$ (LCMO/SRO) bilayers. While Ru–O–Mn superexchange drives antiparallel spin alignment between interfacial Ru and Mn moments, macroscopic antiferromagnetic correlations emerge only within a proper thickness ratio range, consistent with first-principles calculations. Ferromagnetic enhancement—manifested as a significant increase in Curie temperature ($T_{\mathrm{C}}$)—occurs exclusively when LCMO is grown atop SRO, vanishing in the inverse stack. Atomically resolved structural analysis attributes this unidirectional phenomenon to suppressed Jahn-Teller distortions and preferential in-plane orientation of the LCMO crystallographic $c$ axis in the LCMO grown on SRO configuration, which together strengthen double-exchange interactions. Control experiments rule out interfacial charge transfer and Sr interdiffusion as primary mechanisms. These findings establish that stacking-sequence–induced structural asymmetry serves as a dominant control parameter for interfacial ferromagnetism, offering a deterministic route to engineer correlated oxide heterostructures.

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• Magnetic anisotropy
• Magnetic coupling
• Magnetic order
• Structural properties