Background: Providing clinical nursing care to patients with cardiac failure requires the application of the knowledge of the disease process and improves the nursing intervention among internship nurses for improving their practice. Therefore, the training program for the internship nurses’ regarding congestive heart failure patients enables them to build a solid professional career. Aim of the study: This study was aimed to investigate the effect of a training program on internship nurses’ performance regarding congestive heart failure' patients. Research design: Time series quasi-experimental research design was utilized in this research. Setting: The study was conducted at the Cardiac Care Units of Badr and Zagazig University Hospitals, Egypt. Sample: A purposive sample of 100 internship nurses who regularly works with Heart Failure patients. Tools: Knowledge Assessment Structured Questionnaire and an observation checklist for nurses' Practice were used. Results: There was a good improvement in the mean knowledge and practice' score of the internship' nurses after the implementation of the training program compare to pre-implementation. Also, a positive correlation was detected between knowledge and practice' score of the internship' nurses before and after implementation of the training program with statistical significance difference (r=0. 032& r=516) at P-Value (0.032* and 0.001**) respectively. Conclusion: The training program regarding the care of the patients with Congestive Heart Failure (CHF) achieved its aim by improving the internship nurses' performance. In addition, the majority of the CHF patients were satisfied with internship nurses' performance after the implementation of the training. Recommendations: Continuous evaluation is needed to evaluate internship nurses’ performance in Cardiac care settings, especially for patients with CHF. Keywords: Coronary Care Units, Checklist, Humans, Heart Failure, Internship, In-service Training, Residency, Surveys and Questionnaires