Background: Arterial blood gas (ABG) interpretation represents the gold standard method for diagnosis and managing patient oxygenation status and acid-base balance. Aim of the study was to evaluate the effect of educational program regarding arterial blood gases interpretation on nurses’ performance and self-efficacy. Research design: Quasi- Experimental research design (pre and post test). Settings: The study was conducted in general Intensive Care Unit (ICU) and Chest Care Unit at Benha University Hospital, Qalyubia Governorate, Egypt. Subjects: A convenient sample of all available nurses in ICU and Chest Care Unit, (95) nurses from both sexes and agreed to participate in the study. Tools of data collection, Tool (I): Nurses' self-administered questionnaire. Tool (II): Nurses' practice observational checklist regarding arterial blood gases interpretation. Tool (III): Arterial puncture Self-efficacy Scale(APSES). Results: 91.6% of studied nurses had unsatisfactory level of total knowledge about arterial blood gas interpretation preprogram implementation to be significantly improved during immediate and post three months periods of program implementation among (88.4% & 84.2%, respectively). While 93.7% of studied nurses had incompetent level of practice regarding the arterial blood gases interpretation preprogram implementation to be significantly improved during immediate and post three months periods of program implementation among (62.1% & 56.8%, respectively). 67.4% of studied nurses had moderate confidence level regarding the practice of arterial blood sampling preprogram implementation to be significantly improved during immediate and post three months periods of program implementation among(86.3% & 83.2%, respectively).Conclusion: Educational program effectively improved nurses' knowledge, practice and self-efficacy regarding arterial blood gases interpretation .Recommendation: Ongoing educational and training programs for nurses about arterial blood gases interpretation and further study is needed about arterial blood gases interpretation with larger sample size to evaluate its effect on nurses’ performance and patients’ outcomes.