Type 2 Diabetes mellitus, as one of the major universal public health disorders wide spread, requires patients’ lifestyle modulation which would be conducive in dominating blood glucose. The aim of the study was to evaluate the effect of lifestyle modification on glycemic control of type 2 diabetic patients at Suez Canal University Hospitals at Ismailia city. A quasi-experimental design made up of a control group and a study group with pre- and post-test administration was applied. This study was carried out at the Family Medicine Outpatient Clinic and the Diabetic Outpatient Clinic of Suez Canal University Hospitals at Ismailia city in Egypt. 92 type 2 diabetic patients were included in this study. The Diabetes Knowledge Questionnaire; Health promoting lifestyle profile II Scale; and Physical assessment sheet were used for data collection in the two groups. After implementing of the program, those patients who received lifestyle modification intervention achieved better total score of knowledge & knowledge related practice about DM, health promoting lifestyle domains values and glycated hemoglobin, compared with the control group. Factors related to lower glycated hemoglobin in the present study were lower fasting blood sugar level and increasing physical activity. Overall, lifestyle modification program has a positive influence on blood glucose control of patients with type 2 diabetes mellitus. Therefore, it is recommended to that lifestyle modification interventions should be integral part of the curative management of type 2 diabetic patients, and further study in other places to investigate the effect of lifestyle modification on glycemic control of those patients.