Carbon fiber-based electrocatalysts offer significant advantages over conventional powder catalysts, including enhanced active site exposure, superior conductivity, faster reaction rates, lower costs, and improved stability under harsh conditions. In this study, we introduce a rapid and scalable method for spinning carbon-supported metal catalysts into their fibrous forms to achieve uniform catalyst structures that enable roll-to-roll manufacturing. We demonstrate uniform ruthenium (Ru) nanoparticle-loaded carbon fibers by spinning polyacrylonitrile (PAN)-Ru phenanthroline complexes and annealing at 1200 °C for the optimum Ru particle size distribution. We found that the interaction of the Ru complex with the nitrile (−C≡N) group of PAN enabled rheological control and ensured monodisperse Ru confinement. Our investigation of the mechanism details the microstructural evolution during carbonization and oxygen plasma treatment, showing exceptional enhancement in the performance of Ru-embedded carbon fabric electrocatalysts. Ultimately, our rheology-driven spinning protocol bridges the gap between laboratory-scale synthesis and industrial manufacturing of fabric electrocatalysts, providing a versatile platform for nanoconfinement that offers critical insights into the structural evolution of metal–polymer nanocomposites for next-generation energy applications.