Aim: Patients with diabetes can use herbal products to better manage the disease. The aim of this study is to examine the rate of herbal product use and the effect of herbal product use on Body Mass Index (BMI) and hemoglobin A1c (HbA1c) values in patients with diabetes.Method: The descriptive and cross-sectional study was conducted in the diabetes outpatient clinic of a hospital in Istanbul with a total of 104 patients with diabetes. The data were collected using a data collection form, which questioned the patients' socio-demographic characteristics, disease information and herbal product use. Data analysis was performed using Chi-square, One-Sample Kolmogorov-Smirnov test and Mann Whitney U test in computer environment.Results: The mean age of patients with diabetes was 61,08±9,3 years, the mean BMI was 26,3±5,4kg/m², and the mean HbA1c value was 6,9%±1,8%. The BMI and HbA1c values of the patients using herbal products were lower than the patients not using herbal products (respectively; p=,002; p=,047). It was determined that the duration of herbal product use did not affect BMI and HbA1c values (p>,05).Conclusion: The use of herbal products was high in patients with diabetes. It was determined that olive leaf, cinnamon leaf, thyme juice, garlic, black sesame, blueberry, fenugreek seeds, French lavender and bitter almond were used as herbal products. Herbal product use decreased BMI and HbA1c values.