Background: Tobegin aneducationalprogramfor diabetic patients, the assessment of their current level of KNOWLEDGE (K), attitude (A), and PRACTICE (P) was necessary. Objectives: This research aimed to estimate the KNOWLEDGE, attitude, and PRACTICE (KAP) of the general public, because of diabetes mellitus. Methods: A convenient sampling method was used to select 384 of every single person who was admitted to a research, educational and medical center, in the western north of Tehran, in 2018. KAP questionnaire on diabetes was completed, and the level of KAP was evaluated in diabetic and non-diabetic people using SPSS software. Results: The overall mean (, SD) of the KNOWLEDGE, attitude, and PRACTICE was 12. 13, 3. 84, 5. 52, 5 and 10. 68, 51. 96, respectively. Several linear regressions in the two groups for the total KNOWLEDGE scores, total attitudes scores, and total PRACTICE scores displayed several significant (adjusted) associations. Conclusions: The results of this study showed that we need to increase the KNOWLEDGE and attitude of patients with diabetes about a healthy lifestyle, including regular exercise, a healthy diet, and weight loss.