The prevalence of diabetes has been increasing in elderly populations in Taiwan. This systematic review suggests that supplementation with dietary fiber or partial replacement with oral supplements of soy protein could reduce blood glucose in diabetic patients. However, few papers have documented the effect of oral supplements with soy protein and high dietary fiber in elderly diabetic patients. In this study, we hypothesized that oral supplementation with soy protein and high dietary fiber may be beneficial to glycemic control in elderly diabetic patients. Thirty nursing home residents aged 65 years and older were recruited. All participants had been diagnosed with diabetes or met the American Diabetes Association criteria for diabetes screening. This was a 4-month prospective study, which included a 3-month intervention period and a 1-month follow-up period. During the intervention period, an oral supplement was incorporated into the patients' diet to replace 2 snacks a day. The oral supplement provided 500 kcal of energy, 18 g of soy protein, and 25 g of dietary fiber per day. After the intervention, the hemoglobin A1c(HbA1c)level of participants who previously had HbA1c levels of 7% were significantly reduced (8.4% ± 1.4% vs. 7.5% ± 1.5%, < 0.01). In conclusion, taking oral supplements with soy protein and dietary fiber for 3 months can lower the HbA1c level of elderly diabetic patients with higher glucose levels.