Monitoring ICU length of stay (LOS) after CABG and examining its risk factors can guide initiatives on the improvement of care. But few have evaluated this issue to include personal and clinical factors, and demands of ICU care. This study applied Donabedian model to identify risk factors for longer ICU stays after CABG. Lifestyle, clinical factors during and after CABG, TISS were viewed as structure factors, and infection and organ failures during ICU did as process factors. This retrospective cohort study used data via medical records at a medical center. A stratified randomized sample of 230 adults from a cohort of 690 isolated CABGs was to reflect the rate of 34.7% longer than 3-day-ICU LOS. The sample comprised of longer-stay group (n = 150) and shorter-stay group (n = 80). Hierarchical logistic regression analysis revealed that potential signs of infection (3-day average WBC higher than 10,000/μL, OR: 3.41 and the body temperature higher than 38 °C, OR:5.67) and acute renal failure (OR: 8.97) remained as the most significant predicted factors of stay longer than 3 ICU days. Along with higher TISS score within 24 hours (OR:1.06), structure factors of female gender (OR:4.16) smoking(OR: 4.87), higher CCI before surgery(OR:1.49), bypass during CABG (OR:3.51) had higher odds of risk to stay longer. Further quality improvement initiatives to shorten ICU stay after CABG may include the promotion of a smoking cessation program in clinical practice, and better management of the manpower allocation, infection control and renal failure.