A descriptive cross sectional survey was done in tertiary care hospital of Islamabad. The objective of the survey was to assess patients’ knowledge regarding diabetes mellitus (DM), its risk factors, complications, and of management among age range of 18 to 40 years. Our Research was done on relatively younger patients of diabetes. This study was completed on 145 patients (83 males and 63 females), by employing convenience sampling in the outpatient department of Pakistan institute of medical science hospital (PIMS). The structured questionnaire was used to complete the data collection process. Out of 145 participants, (57.2%) were males and (42.8%) were females. Average age of the participants was (34.65) with SD +4.971. Most of the patients were having income less than 10000 PKR (40.6%) per month. The majority of the participants (69%) were not aware about the type of diabetes they have. More than half of the patients identified lifestyle & diet modifications (64.8%) along with glucose level control (65.5%) as most important risk factors for developing complications. The knowledge of diabetes was significantly associated with the educational level and parental history of DM with p-value (0.002) and (0.017) respectively. The other factors gender, age, and income were not statistically associated with knowledge regarding management of diabetes. The patients in Pakistan having diabetes mellitus (DM) had satisfactory level of knowledge in some aspects of the disease. But, overall knowledge related to all aspects of diabetes mellitus (DM) was not up to the mark. The patients need education related to their disease and management.