Highly active catalysts for oxygen evolution reaction (OER) derived from transition metals are crucial for boosting the performance of catalytic electrolysis of water, a key technology for sustainable hydrogen production. This research highlights the design and synthesis of FeM@Co layered double hydroxide (LDH) nanoflowers, where M represents Co, Mn, or Ni, prepared through a facile two-step electrodeposition method. Introducing diverse transition metals significantly modulates the interfacial synergy between the nanostructured Co LDH and the FeM decoration, thereby tuning the electronic structure and electrocatalytic efficiency. Comparative evaluation of the hybrid structures revealed that FeNi@Co LDH nanoflowers exhibit the most remarkable OER activity, with an overpotential of only 266 mV at 100 mA∙cm⁻², a minimal Tafel slope of 21 mV∙dec⁻¹, and excellent durability over 50 h under prolonged operation at 100 mA∙cm⁻². Beyond half-cell studies, a full-cell electrolyzer employing FeNi@Co LDH serving as the anode, with Pt/C functioning as the cathode, delivered 10 mA∙cm⁻² at only 1.43 V, underscoring its high energy efficiency and practical viability. These findings highlight the promise of tailored FeM@Co LDH architectures as high-performance catalysts, contributing valuable knowledge to the purposeful design of advanced materials for efficient water-splitting and clean energy applications.