Diabetes mellitus (DM) has been increasing rapidly in Vietnam. We hypothesized that the main reason may be low fiber intake. Regarding sources, fiber comes mainly from vegetables. However, vegetables popular in Vietnam have low fiber (<2 g fiber/100 g vegetable), so it is difficult to supply sufficient fiber only from vegetables. Therefore, in this study we tried to increase fiber intake a day by using 60 g of Okara foods, containing about 6 g of fiber per day, and assess the effects on the blood glucose levels of DM patients. We contacted 300 type 2 DM outpatients at a hospital and selected 60 of them. We formed 30 pairs matched by gender, age, BMI and years with DM and divided them randomly into an intervention group and a control group. The intervention group consumed about 6 g of fiber from Okara per day for 2 wk. At the baseline and final periods, anthropometric measurements, blood withdrawal and a 3-d weighing method nutrition survey were conducted. Dietary fiber intake increased from 6.9 to 12.6 g ( p <0.01) in the intervention group, but there was no change in the control group. Fasting blood glucose and fructosamine in the intervention group dropped from 6.3 to 5.4 mmol/L ( p <0.05) and from 319 to 301 μmol/L ( p <0.05), respectively but they remained unchanged in the control group. Vietnamese people consumed about 60 g of Okara per day from various menus and increased fiber intake to 6 g/d in 2 wk, which improved blood glucose in DM patients.