This study evaluated the impact of the presence of a certified nurse specialist in critical care (CNS) as ICU head nurse in an open ICU on clinical outcomes. Methods The presence of a CNS as ICU head nurse was implemented in practice in April 2017. To evaluate the impact on patient outcomes before and after the implementation, patients were divided into two groups: before (April 2014 to March 2017; 1988 patients) and after (April 2017 to March 2019; 1664 patients). Patients' demographic data were collected from the ICU database. Results Multivariable logistic regression analysis revealed that the presence of a CNS as ICU head nurse was associated with lower ICU mortality (odds ratio (OR): 0.52, 95% CI: 0.36-0.73, p < .001) and fewer patients receiving mechanical ventilation in the ICU (OR: 0.20, 95% CI: 0.15-0.26, p < .001). Conclusion CNSs are defined as one type of advanced practice nurses. Having a CNS as a head nurse in the ICU may have helped improve patient outcomes by leveraging these practical skills in nursing management.