Background: Ostomy nurses should be able to provide nursing care not only on physiological problems but also other problems related to the ostomy. Aim of the study: To evaluate the effect of nursing instructions on self-care for colostomy patients. Hypothesis: The application of nursing instructions will have a positive effect on self- care for colostomy patients. Research design: Quasi‑experimental study design (pre–post test) was used. Subjects: Thirty adult patients from both sex with abdominal operations treated by colostomy .Setting: The study was carried out at General Surgery Departments of Assuit University Hospital. Tools: (I) Pre-post colostomy knowledge questionnaire ,Tool (II): Pre-post observation checklist for colostomy self-care practices and Tool (III): The Ostomy Self‐Care Index (OSCI). Result: A highly significant statistically difference was found regarding total knowledge, practice and (OSCI) scores of the studied sample pre and post(Immediate and one month) implementation of colostomy nursing instructions (p=.001**). Conclusion: It was concluded that implementation of colostomy nursing instructions had statistically significant positive effect on patient's knowledge and self-care practices. Recommendation: The patients should be included in program provided by ostomy care team for improving self care, prevention and treatment of physical and psychological complications.