Objective: Diabetes is a chronic and common global disease that requires particular care behaviors for the rest of life. People with diabetes can be trained to achieve optimal self-care. The present study was conducted to determine the effect of stage-matched educational intervention on behavior change and glycemic control in elderly patients with diabetes. Matherials and methods: In this controlled clinical trial, 110 type 2 elderly patients with diabetes were selected randomly from health centers in Malard city, Iran, and were assigned to the control and experimental group equally. Data collection instruments were: demographics questions, scales to assess transtheoretical model constructs and stage of change, and blood samples for determining FBS and HbA1c. The mentioned variables were measured before, 1, and 3 months after the stage-matched educational intervention. The educational intervention consisted of 2 group intensive training sessions of about 45 minutes and daily messages via mobile phone for 3 months. The educational topics were about healthy diet and caring behaviors. Data were analyzed using SPSS 25.0 and independent & paired t-test, chi-square, one-way ANOVA, and ANCOVA. The significance level was considered less than 0.05. Results: The mean age of study participants was (66.5 ± 3.91) years. Also, the average duration of diabetes was (7.18 ± 4.21) years, and 50% had a Junior high school education. A significant decrease was found in mean FBS (from 187 ± 43.4 to 136.42 ± 36.34, p < 0.05) and HbA1c (from 8.28 ± 1.26 to 7.26 ± ± 1.10, p < 0.05) in the experimental group, and also the mean of self-care behaviors in the experimental group increased significantly from baseline (from 1.51 ± ± 1.71 to 1.45 ± 0.92, p < 0.05). Conclusions: Educational intervention based on the stages-of-change model can improve glycemic control and behaviors related to controlling diabetes, so it is necessary to pay attention to essential psychological variables in designing educational interventions in order to control blood glucose in patients with diabetes.