Background: Cardiac resynchronization therapy (CRT) uses a device called a biventricular pacemaker that sends electrical signals to both lower chambers of the heart (ventricles). Aim: This study aimed to assess patients' knowledge & practice regarding cardiac resynchronization therapy device. Study design: Descriptive research design was used in this study. Sample: purposive sample includes 190 patients with cardiac resynchronization therapy device. Setting: Outpatient clinics at the National Heart Institute. Tool for data collection: one tool used is composed of four parts, 1st part: interviewing questionnaire including socio-demographic characteristics, 2nd part: Past and current complaints of patients with heart failure, 3rd part: patients' knowledge about heart failure disease and cardiac resynchronization therapy devices, 4th part: patient's reported practice regarding cardiac resynchronization therapy device Results: revealed that, 52.60 % of the patients had total unsatisfactory reported practices while, 74.70 % of the patients had an inadequate level of total knowledge about heart failure disease and cardiac resynchronization therapy device post implementation of a health education program. Conclusion: The current study concludes that the majority of patients had inadequate level of knowledge & unsatisfactory total reported practices regarding heart failure disease and cardiac resynchronization therapy devices. Recommendations: provide health educational programs to all patients regarding heart failure disease and cardiac resynchronization in outpatient clinics at the National Heart Institute.