Background: Diagnostic cardiac catheterization (DCC) is an essential diagnostic procedure for evaluating coronary artery disease and guiding treatment decisions. Although generally safe and well-tolerated, some patients may experience post-procedural complications, pain, and discomfort. Local complications, such as hematoma, infection, and arterial damage, as well as systemic complications like arrhythmia, allergic reactions, and air embolism, can occur and have a negative impact on clinical outcomes and patient satisfaction. Aim of the Study: This study aimed to assess the clinical outcomes and satisfaction levels among patients undergoing DCC. Subjects and methods: A descriptive cross-sectional research design was employed to collect data in this study. Setting: this study was conducted at the cardiac catheterization (CC) unit in the cardiology department of Damanhour Medical National Institute, El-Beheira governorate, Egypt. The study included a convenience sample of 110 adult male and female patients undergoing DCC. Tools: Data collection utilized three tools: Tool I: "Patients' vascular access site assessment sheet," Tool II: "Patients' clinical outcomes post-diagnostic cardiac catheterization assessment sheet," and Tool III: "Patients satisfaction structured interview questionnaire." Results: The results revealed that 67.3% of the studied patients had normal and acceptable vascular access sites pre-DCC, while 59.1% had impaired and severely impaired vascular access sites post-DCC. Most patients reported experiencing pain at both the back and insertion site. 80% of the patients experienced relatively mild post-DCC complications. Furthermore, 95.5% of patients expressed a satisfactory level of satisfaction with their overall experience in the CC unit. Conclusion: While DCC carries a risk of mild negative clinical outcomes, most patients expressed satisfaction with the level of nursing care they received in the CC unit. Recommendation: It is recommended to further investigate the effect of implementing a nursing care protocol on patients' clinical outcomes in those undergoing DCC.