Antiarrhythmic medications are a group of pharmaceuticals that are used to suppress abnormal rhythms of the heart. Cardiac nurses are responsible for preparing and administering antiarrhythmic medications. Aim: The current study aimed to assess nurses' knowledge and practice regarding antiarrhythmic medication at critical care units. Subjects and method: A descriptive study design was utilized to conduct the current study. Subjects: A purposive sample of all available staff nurses working in Critical Care Units at Suez Canal University Hospital (3 Critical Care Units). Tools were collected using an interviewing questionnaire and an observational checklist. Results: Current study result revealed that the mean score of the total nurses' knowledge was (42.03±1.28) out of 45. Also, the total mean knowledge score regarding antiarrhythmic medications was (17.83±. 85) out of 19, while, the mean score of total practice was (25.53±2.08) out of 32. Also, the mean of the administration phase was (15.13±2.37) out of 19. Conclusion: The current study concluded that, although most nurses working in Critical Care Units at Suez Canal University Hospital has a high level of knowledge, they have poor practical skills regarding antiarrhythmic medication. Recommendations: A standard guideline, protocol explaining how to care for patients with life-threatening arrhythmias, and safety of an antiarrhythmic drug, should be available for nurses.