Background: Colostomy is crucial in the treatment of many gastrointestinal problems and has long been one of the procedures that save lives in the globe. Colostomy can be used for many causes as bowel diseases, anastomotic site protection, stool diversion, or a combination of these. Self-care management program is vital for supporting, educating and improving patients' self-care practice with colostomy. Aim: To evaluate the effect of an educational program on self-care management of colostomy patients'. Subject and Method: Design, Quasi-experimental design (one group). Setting: This study was conducted in the outpatient department of Al-Azhar University Hospital, New Damietta City. Subjects: The sample size was 50 patients. Tools: Three tools were used for data collections: Tool I: structure interview questionnaire to assess knowledge of patients' self-care management regarding colostomy care, Tool II: Patient's observational checklist to assess patient practice for colostomy care and Tool III:  Stoma care Self - Efficacy scale to assess coping with difficulties of daily colostomy care. The Results: there was improvement in patients' knowledge, self-care practice and self-efficacy post program implementation with highly significant difference between pre and post program implementation (p<0.005). Conclusion: the educational program had positive effect to improve patients' knowledge, self-care practice and self-efficacy regarding colostomy care. Recommendations: In order to confirm the findings and generalizability, more studies should be conducted on a larger number of colostomy patients.