There is evidence that, in adult cardiac surgical patients undergoing on-pump procedures, tranexamic acid (TXA) dose-dependently increases the risk of convulsive seizure (CS). We aimed to investigate whether a single TXA bolus of 1 g influences the risk of CS in patients who were operated on without the use of cardiopulmonary bypass. In 2249 propensity-score-matched pairs who underwent off-pump coronary artery bypass grafting with or without TXA administration, the risk of CS was 0.5% and 0.3% in the TXA and non-TXA groups, respectively (P = 0.36). In the subgroups of patients with estimated glomerular filtration rates <30, 30–60 and >60 ml/min/1.73 m2, the risk of CS in the TXA group was 2.8%, 1.2% and 0.4%, respectively (P = 0.002), and in the non-TXA group 0.0%, 0.0% and 0.3%, respectively (P = 0.36). The risk of stroke, in-hospital mortality and 30-day mortality did not differ significantly between study groups (P-value >0.05). Our data indicate that in patients undergoing off-pump coronary artery bypass grafting, a single TXA bolus of 1 g generally does not increase the risk of CS. However, the presence and extent of renal insufficiency have a very significant impact on the incidence of CS even after single-dose TXA.