We report a tungsten disulfide (WS ) nanosheet-immobilized hydrogel system that can inhibit oxidative stress on living cells. First, we fabricated a highly stable suspension of WS nanosheets as a radical scavenger by enveloping them with the amphiphilic poly(ε-caprolactone)- b-poly(ethylene oxide) copolymer (PCL- b-PEO) during in situ liquid exfoliation in aqueous medium. After the PCL- b-PEO-enveloped WS nanosheets were embedded in three types of hydrogel systems, including carrageenan gum/locust bean gum bulk hydrogels, physically cross-linked alginate microparticles, and covalently cross-linked PEG hydrogel microparticles, they retained their characteristic optical properties. Intriguingly, the WS nanosheet-immobilized hydrogel particles exhibited sustainable radical scavenging performance without any deterioration in the original activity of the WS nanosheets, even after repeated use. This implies that the hydrogen atoms dissociated from the chalcogen of the WS nanosheets effectively scavenged free radicals through the hydrogel mesh. Because of this unique behavior, the coexistence of the WS nanosheets with living cells in the hydrogel matrix improved cell viability up to 40%, which demonstrates that the WS nanosheets can suppress oxidative stress on living cells.