Inspired by natural metal ion/ligand interactions, stable electrospun hydrogel fibers (EHFs) are produced from polyelectrolyte complexes coordinated with various metal ions. This development provides a novel and promising approach to advance hydrogel fiber applications by creating fibers with high stability in solutions and controlled interfacial reactions. The embedded ions not only improve EHF stability but also act as precursors for fabricating nanoparticles on fibers. The interactions between metal ions and polyelectrolytes dictate metal ion diffusion kinetics. The combination of diffusion and reaction kinetics grants rational and predictable design rules to use EHFs as reactors for nanofabrication.