<p>Magnesium bis(trifluoromethanesulfonyl)amide (Mg(TFSA)<sub>2</sub>)/glyme solutions are promising electrolytes for rechargeable magnesium batteries, but the passivation of the Mg electrode because of the decomposition of [TFSA]<sup>−</sup> anion from the coordination state is a critical issue in practical use. In the present study, functionalized nanofiber gel electrolytes swollen in 0.5 M Mg(TFSA)<sub>2</sub>/triglyme solution were prepared using the silica nanofibers modified with oxymagunesium chloride (–OMgCl) groups (<i>f</i>-SiO<sub>2</sub>NFs) as a gelator. The <i>f</i>-SiO<sub>2</sub>NF gel electrolyte improved the Mg plating/stripping reaction compared to the SiO<sub>2</sub>NF gel without –OMgCl groups.</p>