Background: Patients with type2 Diabetes Mellitus (T2DM) must control their condition by enhancing self-efficacy and following nursing guidelines on compliance to healthy diet, treatment, and lifestyle. Study Aim: This study aimed to evaluate the effect of nursing guidelines on self-efficacy and compliance level among patients with Type 2 Diabetes Mellitus. Research design: A pre-posttest quasi experimental design was utilized. Subjects: A purposive sample of 60 patients. Setting: The study was conducted in outpatient diabetic clinics at Zagazig University Hospital. Data collection Tools: Interviewing Questionnaire for Patients, Self-Efficacy Scale for Diabetes Management, and The Compliance Assessment Questionnaire. Results: 66.7% of studied patients their age <50 years old, 60.0% of them were females and from urban, 70.0% were educated and married. 90% of patients had satisfactory level of self-efficacy after nursing guidelines than before, with a statistical significant difference (P<0.001). Also, 78.33% of studied patients had a good compliance level regarding dietary regimen, treatment, and life style after guidelines than before with a statistical significant difference (P<0.001). A positive correlation was found between self-efficacy and compliance level among studied patients after nursing guidelines with a highly statistical significant differences (P=0.001). Conclusion: It can be concluded that nursing guidelines had a significant positive effect on improving self-efficacy for patients with type 2 Diabetes Mellitus which reflected on improving their level of compliance. Recommendations: It is recommended that nursing guidelines should be established to improve self-efficacy, as it is the most significant factor affecting patients' compliance.