Background and Objectives: Being overweight or obese increases the chances of developing the common type of diabetes, type 2 diabetes. In this disease, the body makes enough insulin but the cells in the body have become resistant to the salutary action of insulin. Information on such public health issues would provide evidence based data to develop guidelines and policies on this subject. The aim of this study was to study the relation between obesity and diabetes mellitus among patient‘s attendants in Erbil city during a period of one year starting from the first of April 2017 to the first of April 2018. Methods: A cross-sectional study included 198 people selected from Erbils outpatient clinics (included two teaching hospitals and two primary health care centers). During a period of one year starting from the first of April 2017 to the first of April 2018. Patient's body mass index ≥ 30 kg/m2 were included in the study. A questionnaire was used to collect the data by face to face interview with the patients. Results: The total number of the sample was 198 people. Their mean age + SD were 43.49 + 11.61 years. The median was 43 years and the age range was 19 to 65 years, (54.5%) of the samples were females, the male: female ratio was0.83:1. The occurrence of diabetes in the studied sample was (18.7%). It increased from (14.3%), to (20.4%), and to (23.3%) among those with BMI of 30-34, 35-39, and ≥ 40 Kg/m2 respectively. Conclusions: There was relation between diabetes and increased body mass index the more the body mass index the more the occurrence of diabetes. The occurrence increased significantly with the age of the studied sample and it is significantly higher among the unemployed and among those who have other medical diseases, it was higher among female. We found non- significant association between diabetes with both exercise and smoking.