We previously reported the preparation of a self-assembled chitin nanofiber (ChNF) film via regeneration from an ion gel with an ionic liquid, 1-allyl-3-methylimidazolium bromide using methanol, followed by sonication and filtration. In this study, the resulting ChNF film was cationized by partial deacetylation and subsequent dispersion in aqueous formic acid, which was then employed as a reinforcing agent for composition with xanthan gum. Xanthan gum hydrogels, which were obtained by exchanging disperse media from xanthan gum ion gels with an ionic liquid, 1-butyl-3-methylimidazolium chloride, were soaked in the cationic ChNF aqueous formic acid dispersions with different degrees of deacetylation (DDAs) to progress composition by ion exchange, to fabricate the ChNF-reinforced xanthan gum hydrogels. The presence of ChNFs in the hydrogels was evaluated by SEM measurement of the lyophilized samples from the hydrogels. The amounts of ChNFs in the hydrogels were depending on the DDA values. The compression testing of the hydrogels indicated the reinforcing effect of ChNFs, which were probably induced by electrostatic interaction owing to anionic nature of xanthan gum.