Aims: The purpose of this study was to investigate the effects of glucosamine (GlcN) on hydrogen peroxide (H2O2)‑induced premature senescence in human retinal pigment epithelial (RPE) cells in vitro. Materials and Methods: We analyzed the cell viability of H2O2‑treated human RPE cells by the 4‑[3‑(4‑iodophenyl)‑2‑(4‑nitrophenyl)‑2H‑5‑tetrazolio]‑1,3‑benzene disulfonate assay. The effect of GlcN on the intracellular levels of reactive oxygen species (ROS) in H2O2‑treated human RPE cells was examined by the fluorescent dye 2′, 7′‑dichlorodihydrofluorescein diacetate. The effect of GlcN on the stress‑induced premature senescence (SIPS) in H2O2‑treated human RPE cells was evaluated by senescence‑associated β‑galactosidase (SA‑β‑Gal) staining. We quantified the effect of GlcN on the protein levels of p21 in H2O2‑treated human RPE cells by western blotting. Results: H2O2 reduced the cell viability of human RPE cells. H2O2 induced the increase of intracellular ROS, whereas GlcN reduced the increase of intracellular ROS due to H2O2 treatment in human RPE cells. GlcN reduced the SIPS in H2O2‑treated human RPE cells and reduced the increase of the p21 protein level in H2O2‑treated human RPE cells. Conclusions: GlcN attenuates the oxidative stress caused by H2O2 on the increase of ROS and the induction of SIPS in human RPE cells, at least in part, by suppressing the p21 pathway. These effects may contribute to the GlcN‑mediated antioxidative effects in the eye in age‑related macular degeneration.