Pediatric cardiac catheterization is applied for diagnostic and therapeutic procedures to children with congenital and acquired heart diseases. Aim: To evaluate the effect of educational guidelines on mothers' emotional status regarding children undergoing cardiac catheterization. Design: A quasi-experimental research design with a pre-and post-test was used. Setting: The study was conducted at the intensive care, catheterization, and cardiac care unit at Sohag University Hospital. Subjects: A convenient sample of 70 mothers of children who diagnosed with cardiac defects undergoing cardiac catheterization was involved in the current study. Tools for data collection Two tools were used in the current study first tool was mothers’ interviewing questionnaire (pre/post), which included demographic characteristics; and mothers’ knowledge regarding cardiac catheterization and second tool was Depression, Anxiety, and Stress Scale (DASS). Results: After implementation of the guidelines, significant relationship and improvements were detected between mothers' knowledge about their children's cardiac catheterization than before and mothers' emotional status (stress, depression, and anxiety levels) were severe before implementation of the guidelines while these levels become low after guidelines implementation. Conclusion: The guidelines for mothers of children undergoing cardiac catheterization had a positive effect on improving their knowledge and minimizing mothers' emotional disturbances like depression, anxiety, and stress regarding their children's cardiac catheterization after implementation of the guidelines than before. Recommendations: The guidelines for mothers of children undergoing cardiac catheterization should be conducted to raise their awareness. Psychological support and intervention activities should be carried out to help mothers to become emotionally stable