Background: Temporary cardiac pacing provides electrical stimulation to a heart compromised by disturbances in the conduction system causing hemodynamic instability. The use of a temporary pacemaker to treat a brady dysrhythmia or in some cases, a tachydysryhthmia, is undertaken when the condition is temporary and a permanent pacemaker is not necessary or available in a timely fashion. Temporary cardiac pacing is utilized in acute situations and for critically ill patient populations requiring immediate therapy. Aim: The present study was conducted to assess nurses' knowledge and practice regarding safety of patients with temporary cardiac pacemakers in the critical care units. Research design: A descriptive exploratory design. Setting: This study was conducted at intensive and coronary care units at National Heart Institute affiliated to Ministry of Health. Methods: A purposive sample of 50 nurses working in the coronary care units at National Heart Institute, 50 nurses from both genders, with different ages, educational levels and years of experience was selected for this study. Data were obtained through two main tools; self administered questionnaire tool and observational checklist. Result: Nearly three quarters of the study nurses had unsatisfactory level of knowledge and incompetent levels of practice regarding care of patients with temporary cardiac pacemaker in the critical care units. There was a statistical significant relationship between demographic characteristics (age of the studied subjects, education, years of experience and training courses) regarding to total knowledge and practice of the studied subjects. While there was a statistical significant relationship between total practice levels of the studied subjects regarding to total knowledge of the studied subjects. Conclusion: The study concluded that, there are several factors affecting the knowledge and practice of the studied nurses including demographic factors (e.g. age, years of experience, level of education and attendance of training courses), in addition to the organizational factors (e.g. availability of resources, hospital policy and setting) as well as personal factors (e.g. presence of well trained and highly educated team leader and presence of competent team member). Also it was found that the knowledge level of the studied nurses was affecting their practice. Recommendations: Further study to evaluate the reflection of educational program regarding nurses' performance &consequently on the patient outcome. The study should be replicated on large sample &in different hospitalssetting in order to generalize the results.