In this study, we aimed to investigate the antioxidant and immunopotentiating effects of leaves of cherry elaeagnus (Elaeagnus multiflora, Em). The leaf, stem, and root of Em have been used in Kampo medicine. There are data on the therapeutic effects of Em fruit, but no information on its leaves. We thus investigated the antioxidant and immunopotentiating effects of Em leaf extract. Balb/c mouse spleen cells were treated with concanavalin A and hot aqueous Em leaf extract (50, 100, and 200 µg/mL), and the effects on spleen cell proliferation and the secretion of interleukin (IL)-2, IL-4, and IL-10 were evaluated. A concentration-dependent increase in the secretion of IL-2 and IL-4 cytokines was observed, with concentrations of 1.86 pg/mL of IL-2 and 37.63 pg/mL of IL-4 when cells were treated with 200 µg/mL of the extract. Natural killer (NK) cell activity was determined based on a co-culture of spleen cells and Yac-1 cells. NK activity gradually increased in a concentration-dependent manne. Further, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity was 58.5% and 2,2ʹ-azino-bis(3-ethylbenzothiazoline-6sulfonic acid) radical scavenging activity was 78.2% with an extract concentration of 200 µg/mL. The high antioxidant activity of the hot water extract of Em leaves suggests their potential therapeutic value and warrants further studies.