Cardiac catheterizations are common procedures among patients with cardiovascular diseases. Aim of the study: Assess the effect of health education guidelines to prevent complications associated therapeutic cardiac catheterization at Specialized Medical Hospital of Mansoura University. Method: A quasi-experimental research designwas utilized to accomplish this study. Subjects: included 75 patients undergoing therapeutic cardiac catheterization who admitted in the cardiac catheterization unit. Tools: Three tools were used for data collection; Patient's Assessment Sheet, assessment sheet of therapeutic cardiac catheterization procedure and assessment of patient's condition after the procedure and a questionnaire sheet for patient's health educational needs. Results: The study revealedbefore implementing the health education guidelines,(92.0%) of the patients had poor total knowledge score level. On other hand, (53.4%) of patients had good total knowledge score level while, only (10.6%) of patients had poor total knowledge score levelafter implementing the health education guidelines. There was a statistical significant difference (p < 0.05) between patient'stotal knowledge score levels and patient's total habits after implementing health education guidelines. Recommendations: Reinforcing follow-up education that focus on lifestyle modification for patient with therapeutic cardiac catheterization in outpatient clinics.