Background and Aims: Recent studies have brought evidence on the connection between excess weight and suboptimal glycemic control for Diabetes Mellitus (DM) patients. The aim of this study was to evaluate the association between increased Body Mass Index (BMI) and the likelihood of having suboptimal glycemic control in patients with Type 1 and Type 2 Diabetes Mellitus. Materials and Methods: A case-control study was conducted on 662 patients suffering from Diabetes Mellitus and statistical analysis was performed in order obtain evidence associating BMI and poor glycaemic control. We defined as increased BMI, values >25 kg/m2 and a hemoglobin A1c (HbA1c) value >7% reflected suboptimal glycemic control. Results: 559 (84%) patients had HbA1c >7%. 550 (83 %) patients had a BMI >25 kg/m2. In case of HbA1c >7%, a BMI >25 kg/m2 was found in a number of 457 patients (82 %), whereas a normal BMI was present in 102 (18%) patients. For the HbA1c<7% cases, the number of patients associating BMI >25 kg/m2 was 93 (90%) and a normal BMI was present in 10 (10%) patients. BMI >25 kg/m2 was not associated with a higher probability of having above-target HbA1c values compared to patients with target HbA1c (OR 0.48, 95% CI: 0.24 to 0.95), with a statistically significant p <0.05. Conclusions: The findings revealed that although in case of suboptimal glycemic control, the number of patients who had a BMI >25 kg/m2 was significantly higher than the number of patients with a BMI < 25 kg/m2, a BMI above target was not associated with greater odds of having HbA1c higher than the standard 7% level, compared to individuals with normal HbA1c levels. The results emphasize that a multitude of factors are involved in the process of achieving a targeted glycemic control and a stepped-care approach should be considered for optimum management of Diabetes Mellitus.