This study was performed to investigate the in vitro and in vivo anticancer effects of persimmon leaf extracts on human gastric cancer cells. In vitro anticancer effects of persimmon leaf extracts (water extract at 8$0^{circ}C$ for 3 hours, water extract at room temperature for 48 hours, 50% ethanol extract at 8$0^{circ}C$ for 3 hours, 50% ethanol extract at room temperature for 48 hours, 75% ethanol extract at 8$0^{circ}C$ for 3 hours and 75% ethanol extract at room temperature for 48 hours) on SNU16 (Korean gastric cancer cell) were investigated by MTT assay. Persimmon leaf extracts exhibited strong in vitro anticancer effects. We found that the higher the ethanol content of the solvent, the stronger the in vitro anticancer effects. Extraction yields, contents of flavonoids, vitamin A, vitamin C and vitamin E were measured. We found that the higher the ethanol content of the solvent, the higher the extraction yields and the contents of flavonoids, vitamin A and vitamin E. Among persimmon leaf extracts, 75% ethanol 8$0^{circ}C$ extract showed the highest extraction yield, the highest contents of flavonoids, vitamin A and vitamin E and exhibitied the strongest in vitro anticancer effect on SNU16. Therefore, 75% ethanol 8$0^{circ}C$ extract was chosen as the material to investigate in vivo anticancer effects. In vivo anticancer effect of persimmon leaf 75% ethanol 8$0^{circ}C$ extract was investigated in SNU16 transplanted nude mice. Twenty five female nude mice (BALB/c) were blocked into five groups according to body weight and raised for 4 weeks with diets containing 4% (w/w), 8% (w/w) persimmon leaf 75% ethanol 8$0^{circ}C$ extract, with IT (intratumoral) injection treatment with 1.65 mg/100 $mu$1, 3.3 mg/100 $mu$1 concentration every other day 3 weeks after SNU16 was transplanted. Persimmon 75% ethanol 8$0^{circ}C$ extract significantly lowered tumor weight and tumor volume in SNU16 transplanted nude mice. Tumor weight and tumor volume in all experimental groups were significantly lower than those in the control group. Helper T cell (CD4) levels of mice injected with 3.3 mg/100 $mu$1 extract significantly increased. Cytotoxic T cell (CD8) levels in all experimental groups significantly increased and helper/cytotoxic T cell ratios in all experimental groups significantly decreased. Natural killer cell and MHC class II molecule in all experimental groups significantly increased. In conclusion, persimmon leaf 75% ethanol 8$0^{circ}C$ extract exhibited strong in vitro and in vivo anticancer effects against SNU16 cells and it increased cytotoxic T cell, natural killer cell and MHC classII molecule in experimental groups in SNU16 transplanted nude mice.