Functional tricuspid regurgitation (FTR) is defined as abnormal systolic tricuspid leakage with normal valve structures, and its prognostic role and management in patients with left-heart valve disease is well known. Due to paucity of data on FTR in patients with ischemic heart disease, the aim of our prospective study was to compare the prognostic effect of FTR between patients with moderate FTR and those with less-than-moderate FTR undergoing isolated coronary artery bypass graft (CABG) surgery. This prospective cohort study included all the patients who were candidate for isolated CABG and were referred for preoperative transthoracic echocardiography between April 2018 and November 2018. Patients were categorized into two groups: less-than-moderate FTR and moderate FTR. The endpoints of the study were the prognostic effect of FTR on short-term mortality and morbidities as a composite endpoint, as well as length of hospitalization, length of intensive care unit (ICU) stay, and ventilation time. Of a total of 410 patients, 363 patients (mean age = 62.4 years, 63.7% men) entered our final analysis. Logistic regression analysis demonstrated that composite endpoints of short-term mortality and morbidities was not significantly different between the two groups, but moderate FTR had a statistically significant effect on length of hospitalization (P = 0.002) and the ventilation time (P = 0.048). This effect, however, did not persist after adjustments for probable known confounders. Our study indicated no significant prognostic effect for preoperative FTR versus less-than-moderate FTR on short-term mortality and morbidities, as well as length of hospitalization, length of ICU stay, and the ventilation time.