Fluid and electrolyte imbalance in the patient with cardiovascular dysfunction is a common complication of cardiac disease. Cardiovascular diseases remain the number one cause of death i today. Recovery from these diseases requires careful attention to the factors that influence heart status. Fluid and electrolyte imbalance in the cardiac patient often is both life-threatening and preventable. Maintaining a homeostatic environment in terms of fluid and electrolyte balance is critical to achieving optimal cardiac function in all heart patients. Aim of study: to evaluate the effect of nursing intervention program on maintaining fluid and electrolyte balance among patients with congestive heart failure. Subjects and Methods: This quasi-experimental study was conducted in the outpatient clinics of the cardiology department at Zagazig University Hospitals on 60 patients suffering from CHF. The tools used in data collection were an interview questionnaire form for knowledge and observation checklists for practice, in addition to an input/output sheet. The researcher prepared the educational health promotion program, implemented it, and measured its immediate and 3-month follow-up effects. Results: Patients’ age ranged between 33 and 85 years, with 55.0% males. Patients’ knowledge improved from 3.3% pre-intervention to 81.7% post-intervention phase, and 75.0% at the follow-up (p<0.001). Their practices improved from 1.7% pre-intervention to 81.7% post-intervention, and 75.0% at follow-up (p<0.001). The prevalence of edema decreased from 73.3% pre-intervention to 26.7% at follow-up (p<0.001). In multivariate analysis, the study intervention was the main positive predictor of the knowledge and practice scores.