Background: Diabetes mellitus (DM) is a chronic progressive metabolic disorder. According to International Diabetes Foundation (IDF) estimation in 2019, globally 463 million adults have diabetes among the population aged 20-79. If this trend continues, 700 million of people will have diabetes by 2045, and the larger increases will occur in low- and middle-income countries. In Mongolia, the prevalence of Diabetes 5.4%. Regularly assessing the quality of life (QOL) in the control of patients with diabetes is important to evaluate the effectiveness of management, to plan treatment and thus to improve monitoring. Meaningful. The purpose of our study was to evaluate the Validity and Reliability of the Mongolian Version of the World Health Organization’s Quality of Life Questionnaire (WHOQOLBREF) in patients with Type 2 Diabetes. Methods: The cross sectional survey was conducted in Ulaanbaatar. For the study 150 patients with T2DM were recruited, who have met the inclusion criteria and agreed to the informed consent. In the study, self-management control, beliefs about illness, depression were assessed. Additionally, anthropometric measurements, blood pressure (BP), levels of glucated hemoglobin level (HbA1C), lipids and fasting blood glucose (FBG) at the baseline and after 3 months follow ups were measured. Statistical analyses was performed using SPSS 21 software. Results: The study involved newly diagnosed Type 2 diabetes with mean age of 49,4±8,9 years. 65 men (43,6%), 85 women (56,7%) and 39,3% of the participants had a family history of diabetes. The Cronbach’s alpha for analysis of the reliability of the WHOQOLBREF was a=0.74-0.84. The patient’s fasting blood glucose FBG, HbA1c, and low-density lipoproteins (LDL) were statistically significantly higher (p <0.05) than normal and the triglyceride (TG) was increased, but it was not statistically significant (p> 0.05). The mean TG had statistically significant (p <0.05) increase by sex. There is a need for further study of the specific questionnaire of QOL people with diabetes. Conclusion The Mongolian version of the WHO Quality of Life Questionnaire evaluating diabetes patients, the internal consistency of the questionnaire was reliable and the validity was a = 0.74-0.84.