Thesis Abstract: Background: cardiac arrest (CA) is an emergency that requires immediate cardiopulmonary resuscitation by qualified health care provider (AHA, 2021). Nurses are the first line receive CA victims. Therefore, it is very essential to ensure nurses competencies in performing resuscitation. Aim: This study aimed to evaluate the effectiveness of Basic Life Support simulation-based training program on primary health care nurses' knowledge, skills, and self-efficacy about Cardiopulmonary Resuscitation. Methodology: Quantitative pretest posttest single group quasi experimental design was employed in the study. Convenience sampling technique applied by recruiting 76 nurses from three health centers in Bahrain. During pre-test, questionnaires were distributed by the researcher to assess CPR knowledge & self-efficacy. Participants' skills of CPR were evaluated by using the skills checklist. Clinical simulation provided by a certified instructor to participants. After that, a post-test was given same as the pre-test. Results: the results of the pre-test showed moderate level of knowledge (59.2%), skills (67.1%) and self-efficacy (40.8%) regarding CPR among primary health care nurses. The results showed significant improvement in CPR knowledge (75%), skills (100%), and self-efficacy (92.1%) among all the participants in pre-post test (P<0.001). Conclusion: The clinical simulation program provided by qualified instructor improves theoretical knowledge, practical skills and self-efficacy of nurses. Keywords: Primary Health Care, Nurses, Cardiopulmonary Resuscitation, Knowledge, Abilities, and Self-Efficacy. Recommendations: Similar studies should be conducted among higher sample size, adding two groups when experimental studies are conducted and longitudinal follow ups are recommended.