High-sensitivity cardiac troponin I (hs-cTnI) is a widely used biomarker to identify ischemic chest pain in the Emergency Department (ED), but the clinical impact on emergency coronary artery bypass grafting (eCABG) remains undetermined. We aimed to evaluate the clinical impact of hs-cTnI measured at the ED by comparing outcomes of eCABG in patients with non-ST-segment-elevation acute coronary syndrome (NSTE-ACS) which comprises unstable angina (UA) and non-ST-segment-elevation myocardial infarction (NSTEMI). From January 2012 to March 2016, 242 patients undergoing eCABG were grouped according to serum hs-cTnI level in the ED. The primary endpoint was major cardiovascular cerebral event (MACCE) defined as a composite of all-cause death, myocardial infarction, repeat revascularization, and stroke. The incidence of each MACCE composite, in addition to postoperative complications such as acute kidney injury, reoperation, atrial fibrillation, and hospital stay duration were also compared. Patients were divided into two groups: UA [<0.04 ng/mL, n = 102] and NSTEMI [≥0.04 ng/mL, n = 140]. The incidence of MACCE did not differ between the two groups. Postoperative acute kidney injury was more frequent in the NSTEMI group after adjusting for confounding factors (6.9% vs. 23.6%; odds ratio, 2.76; 95% confidence interval, 1.09-6.99; p-value = 0.032). In-hospital stay was also longer in the NSTEMI group (9.0 days vs. 15.4 days, p-value = 0.008). ECABG for UA and NSTEMI patients showed comparable outcomes, but hs-cTnI elevation at the ED may be associated with immediate postoperative complications.