Like adults, children often experience anxiety associated with medical procedures .Aim: To assess the effect of psychological preparation program on anxiety of children undergoing endoscopy. Method: A true experimental research design (pre- test, post - test control design) was used for this study. The study was conducted in pediatric endoscopy unit at Assiut university children hospital, Egypt. A total of 70 children were enrolled in this study divided into two groups (study and control groups with 35 children in each group). Three tools were used to collect data in this study: Tool 1: a structured questionnaire. Tool 2: State trait anxiety inventory. Tool 3: The psychological preparation program consisted of demonstration of materials that would be encountered during the procedure. Results: The anxiety state mean score had reduced in the study group compared to that in the control group after implementation of the program and after implementation of the program compared to that before its implementation in the study group. Conclusion: A significant reduction of anxiety level was apparent for children undergoing endoscopy procedure after receiving the preparation program.