Aim. To comparably assess the perioperative risk factors that differentiate off-pump coronary artery bypass (OPCAB) grafting cases from those sustaining unplanned conversion to on-pump beating heart (ONCAB/BH) approach, in patients with left ventricular ejection fraction (LVEF) < 40%. Methods. Perioperative variables were retrospectively assessed in 216 patients with LVEF < 40%, who underwent myocardial revascularization with OPCAB (n = 171) or ONCAB/BH (n = 45) approach. The study endpoints were operative mortality (30-day) and morbidity assessed by length of intensive care unit stay (LOS-ICU), using 2 days as cut-off point. Results. Poor LVEF, increased EuroSCORE II, acute presentation, congestive heart failure, cerebrovascular disease, perioperative renal impairment, clinical status deterioration upon admission and during ICU stay, acute myocardial infarction, and low cardiac output syndrome supported by inotropes and/or balloon-pump counterpulsation were significantly related to ONCAB/BH group (P < 0.05). EuroSCORE II (P = 0.01) and LVEF (P = 0.03) were the most powerful discriminative predictors of intraoperative conversion to ONCAB/BH. Operative mortality was 2.9% in OPCAB and 6.6% in ONCAB/BH group (P = 0.224), while 23.4% participants in OPCAB and 42.2% in ONCAB/BH approach had a LOS-ICU > 2 days (P = 0.007). Conclusions. Patients with LVEF < 40% undergoing ONCAB/BH are subjected to more preoperative comorbidities and implicated ICU stay than their OPCAB counterparts, which influences adversely short-term morbidity, while operative mortality remains unaffected.