INTRODUCTION: Type 2 diabetes mellitus (T2DM) is one of the most prevalent non-communicable diseases globally. This study aimed to determine the association between body mass index (BMI) and diabetes mellitus (DM) control among patients with T2DM. METHODS: A retrospective study was conducted from October 2023 to June 2024 using secondary data from the National Diabetes Registry (NDR) of Muar District Health Office, Johor. Patients with T2DM registered in the NDR and audited from 2021 to July 2023 were included. The association between BMI and DM control was analysed using hierarchical multinomial logistic regression. RESULTS: A total of 1955 patients were included in the study. The prevalence of good, intermediate and poor BMI control was 38.8% (95% Confident Interval (CI)=36.7, 41.0), 22.2% (95% CI=20.3, 24.0) and 39.0% (95% CI=36.7, 41.2), respectively. Most patients were older Malay women. There was an association between BMI and DM control unadjusted (P<0.001) and adjusted for several confounding factors using seven models (P=0.003-0.034). The R value also improved from 0.008 to 0.293. Conclusion: Among patients with T2DM, a higher BMI, the creatinine level and medications such as glucose-lowering drugs, ticlopidine, acetylsalicylic acid and statins are associated with DM control. However, as the study design does not allow for the assessment of causality or progression over time, the findings should be interpreted as descriptive associations rather than as evidence of cause-and-effect relationships. Focus on medication compliance, healthcare providers' role during medication consultation and stakeholders' role in maintaining drug supplementation is needed.