Background: In this 21st century, the need for health services continues to experience rapid changes, telemarking is delivering nursing care and conducting nursing practice by using technology. The recovery after one day surgery is often troublesome for mothers often feel insecure regarding optimal post-operative care for their children after discharge from hospital. Aim: The present study aimed to evaluate the effect of telenursing program on mothers' knowledge about postoperative care for one day surgery children. A quasi-experimental research design (pretest/post-test design) was utilized in the present study. The study was conducted at three pediatric hospitals affiliated to Cairo University. Subjects and method:  A purposive sample of 60 mothers and their children from the previously mentioned settings were included in the study and divided equally to study and control group. Tools of data collection included three tools: a structured interview questionnaire sheet to assess mothers and their children's personal characteristics; assessment sheet of mothers' knowledge about one day surgery postoperative care and follow up phone call record form. Results: The results of this study indicated highly statistically significant differences concerning mothers' knowledge preimplementation/post implementation of telenursing intervention program Conclusion: The study concluded that telenursing intervention program positively improved mother's knowledge in study group after implementation than before. Recommendation: Telenursing intervention program should be established to improve mothers' knowledge about post-operative care for one day surgery children.