Green-plant membrane is a phytonutrient present in green leafy vegetables at high concentration. Postprandial increases in blood triglyceride levels result in insulin resistance and type 2 diabetes. Additionally, dietary life and eating order also affect postprandial hypertriglyceridemia. In this study, the effects of once-daily intake of green-plant membrane with dietary oil on postprandial hypertriglyceridemia were investigated in vitro and in vivo. In vitro, green-plant membrane bound hydrophobic bile acids but did not inhibit pancreatic lipase activity. Following the administration, green-plant membrane with dietary oil in rats, oral fat tolerance tests, increases in serum triglycerides levels were significantly reduced. Moreover, fecal total lipid and bile acid volumes were significantly increased in rats that administered 200 mg/mL green-plant membrane. These results suggest that green-plant membrane with dietary oil inhibits dietary fat absorption via promotion of bile acid excretion in feces and the effectiveness of eating green-plant membrane, such as green leafy vegetables, with meals.