Objective Te patients’ knowledge and attitudes in the self-management of diabetes mellitus, which is a global health problem that can cause serious morbidity and mortality, is of vital importance. Tis study aimed to determine the knowledge and attitude levels of patients with type 2 diabetes and to evaluate related factors. Materials and Methods Tis descriptive and cross-sectional study was conducted between April 9 and June 9, 2019 in 149 type 2 diabetes patients who presented to the outpatient diabetes polyclinic of internal medicine clinic of T.R. Ministry of Health Sakarya University Training and Research Hospital. In addition to the personal information form and diabetes information level questionnaire prepared by the researchers, Diabetes Attitude Scale was administered to the patients by self-filling method under the supervision of the researcher. Te obtained data were evaluated statistically. Results Te mean age of the patients was 54,82 years ±10,74 SD and the mean disease duration was 9,51 years ±6,86 SD. Te mean score of the patients from the diabetes knowledge level questionnaire was 74,39±11,40 SD out of 100, and the mean attitude score from the Diabetes Attitude Scale was 3,99±0,30 SD. Significant diferences were found between diabetes knowledge levels in terms of disease duration (p=0,006), education level (p<0,001) and alcohol use status (p=0,010). In terms of smoking status (p=0,015), there was a significant diference between diabetes attitude levels. It was observed that there was a statistically significant relationship between the scores obtained from the diabetes knowledge level questionnaire and the scores obtained from the Diabetes Attitude Scale (p=0,002; r=0,249). Conclusion Tere is a need for more efective and comprehensive training programs which are updated by taking into account the deficiencies and the disadvantaged groups in order to increase the knowledge level of the patients about diabetes and to develop positive attitudes.