Background: Negative pressure wound therapy is a promising treatment post cardiothoracic surgery especially for patients with deep sternal wound infection. Appropriate wound care requires the integration of knowledge and skills to enhance the healing process and improve patient outcomes.  Aim: To evaluate the effectiveness of applying nursing care protocol regarding negative pressure wound dressing on clinical outcomes of patients undergoing cardiothoracic surgeries. Design: A quasi-experimental design was utilized. Setting: Cardiothoracic Surgery Department and outpatient clinic at the Cardiothoracic and Vascular Surgery Center, Mansoura University Hospitals, Egypt. Subject: A Purposive sample composed of (64) patients and (21) nurses. Tools: The researchers used three tools to collect the data; Tool 1, a structured interview questionnaire, divided into three parts for assessing nurses' demographic and professional data in addition to assessing patients' demographic and medical data, and the nurses' knowledge questionnaire. Tool II: Observational checklist to assess nurses' practice regarding negative pressure wound dressing. Tool III: Bates-Jensen Wound Assessment tool.  Results: There was a significant improvement in nurses' knowledge and practices after applying the nursing care protocol regarding negative pressure wound dressing. Also, there were significant differences between patients in the study and control groups regarding severity levels of the wound, as most of the patients in the study group had minimal wound severity with better wound condition compared to the control group. Conclusion: Applying nursing care protocol regarding negative pressure wound dressing has demonstrated significant effectiveness in improving clinical outcomes for patients undergoing cardiothoracic surgeries. Recommendations: Implementing a standardized nursing care protocol for negative pressure wound dressing across all cardiothoracic surgery units to ensure consistency in patient care and improve clinical outcomes.