Acute coronary syndrome refers to a range of potentially life-threatening conditions that affect the coronary artery blood supply to the heart. It is associated with increased patient mortality, length of hospital stay and health care costs. Clinical pathways are now one of the main tools that used to manage the quality in healthcare concerning the standardization of care processes. Hence, the aim of this study is to evaluate the effect of implementing a clinical pathway guideline on the clinical outcomes of patients with acute coronary syndrome. A quasi experimental research design was utilized in this study and it was conducted on 60 adult patients at the Cardiac Intensive Care Unit of Tanta University Hospital. The patients were divided into two groups (control and study group) 30 patients in each. The control group: non-clinical pathway group involved patients receiving the routine management regimen while the study group: clinical pathway group (CP group) involved patients who received management according to the clinical pathway guidelines. The findings of this study revealed that a significant changes among control and study group from admission to discharge regarding mean scores of body temperature, Pulse and respiration rate where P<0.05. There was significant increased mean score of central venous pressure among control group compared to study group on admission, after 2 hrs and on 2 nd day of admission with P=0.013, 0.007 and 0.001, respectively. The present study showed that low percentages (20.0 %) of control group had cardiogenic shock compared to none patient in the study group with a significant difference between two groups, where P=0.012. Insignificant difference was observed between control and study group regarding duration of stay in ICU and status of patients on discharge with P=0.075 and 0.206. Also it was noticed that the level of reduction of the mean of Hamilton Anxiety Score in the study group was higher than its level in the control group on discharge. It can be concluded that the established pathway achieved its goal of, improving physiological parameters and decreasing patient's complications, length of stay, and anxiety levels. Based on the findings of this study, the following recommendations are suggested; clinical pathway should be implemented routinely for patients with acute coronary syndrome. Integrating ACS clinical pathway into plan of care to replace the traditional nursing care plan.