Background: Safety from harm and injury in receiving health services is a human right. Nurses play a key role in enhancing the quality and safety of care through recognition, management and reporting of issues that have, or could have, a negative impact on patient outcomes. Aim of the study: This study aimed to assess nurses' knowledge, attitude and interpretation of waves regarding safety of patient connected with intra-aortic balloon pump. Research design: A descriptive exploratory research design was used. Setting: This study was conducted at the cardiothoracic intensive care units at Ain-Shams University and Nasser Institute for Research and Treatment. Subjects: Convenience sample of 65 nurses. Tools: Three tools were used; tool (1) nurses' structured interviewing questionnaire, tool (2) attitude likert scale and tool (3) intra-aortic balloon pump interpretation form. Results: 64.6% and 69.2% of the studied nurses had unsatisfactory level of knowledge and waves' interpretation regarding safety of patient connected with intra- aortic balloon pump respectively. While, 56.9% of them had positive attitude regarding safety of patient connected with intra-aortic balloon pump. Furthermore, there was a highly statistically significant positive correlation between nurses' knowledge, safety attitude and intra- aortic balloon pump waves' interpretation. Conclusion: More than two thirds of nurses under study had unsatisfactory knowledge level, more than one half of them had positive safety attitude and more than two thirds of them had unsatisfactory level of safety interpretation regarding IABP waves. Recommendation: Providing educational training programs for nurses regarding intra- aortic balloon pump and safety interpretation of intra- aortic balloon pump waves.