Background and study aim: Diabetes is a self managed disease and the participation of the individual, health care team and his family is very essential in managing the disease and preventing its complications.The aim of study was to evaluate the effectiveness of a self-management support program on improving Knowledge and practices of patients with diabetes mellitus at Zagazig University Hospital. Subjects and Methods: A quasi experimental research design was used in this study. A purposive sample of 70 patients with diabetic foot patients were randomly assigned to either the control (n= 35) or the study (n= 35) group using matched criteria of foot ulcer history and foot problems. Three tools were used for collection of data, patient's assessment questionnaire, questionnaire about patient knowledge about diabetes mellitus and foot care and self reported practice questionnaire. Results: The study finding revealed that sixty (60.0%) of patients in the study and control groups were males with more than 40 years of age with Mean±SD (52.7±8.8 and 53.5±7.8 respectively), there was statistical significant relationship between patient knowledge and practice where more than three quarters (89.6%) of patients who had unsatisfactory knowledge had inadequate practice. Also there was positive correlation between foot care score and knowledge score and practice score. Conclusion: The self-management support program showed an improvement in patients' knowledge which reflected an improvement on their practice and diabetic foot care behaviors in post phase. It is Recommended to increase awareness and prevent the diabetic foot and its complications by apply nursing intervention programs regarding importance of foot care and to impart knowledge on foot care, use media to motivate diabetic patient for monthly diabetic clinic visiting, use media to increase awareness about the diabetic foot, continues follow up for patients who is suffering from the diabetic foot and increase distributing free handbooks that are specific for diabetes in the public places.