Background: Coronary artery bypass grafting (CABG) may be performed with or without cardiopulmonary bypass (CPB). The Society of Thoracic Surgeons (STS) provides a preoperative risk assessment tool for CABG and reports postoperative outcomes from a database that is updated quarterly. This manuscript aimed to analyze the preoperative risk and postoperative outcomes in a subset of CABG patients with ejection fraction < 40% utilizing a pump-assisted beating-heart technique. These study results were compared to the STS risk calculator and database. Methods: A single-center observational study of 108 patients undergoing pump-assisted direct coronary artery bypass (PAD-CAB) surgery with an ejection fraction < 40% were examined. All patients were evaluated preoperatively with the STS risk assessment calculator. Postoperative outcomes were compared with the expected outcomes using the Wilcoxon signed-rank test and the area under the receiver operating characteristic curve (AUC). Results: The STS-predicted rates for mortality (3.3% vs 2.7%, P = 0.11) and composite morbidity or mortality (21.4% vs 7.4%, P < .001) were higher than the observed. STS showed poor discriminatory power for mortality (AUC = 0.48), reoperation (AUC = 0.48), morbidity (AUC = 0.51) and prolonged length of stay (AUC = 0.62). Discussion: PAD-CAB results compare favorably to the STS database predicted outcomes for CABG. However, comparison of the study group to STS is problematic because specific STS risk calculator definitions are subjective, and database outcomes do not consider the technique of PAD-CAB. Further refinements in these areas are necessary.