Methylglyoxal is a reactive α, β dicarbonyl aldehyde compound that originates from various biochemical pathways. Some studies suggest that increased methylglyoxal in blood leads to changes in fibrinolysis; however, the precise mechanism is not clear. The aim of this study was to compare different concentrations of methylglyoxal and aspirin on fibrinolysis in the plasma of healthy individuals in vitro. Different concentrations of methylglyoxal (5, 50, 100, and 500 μmol/l) and aspirin (1, 10, and 100 mg/l) were added to the plasma citrate. They were incubated at 37°C for 24 h. Then, fibrinolysis parameters were analyzed by the turbidimetric procedure at 405 nm. The Independent Samples t-test was utilized to compare them (P < 0.05). Findings revealed that methylglyoxal at 500 μmol/l with aspirin 100 mg/l had significant changes in the maximum lysis velocity (0.163 ± 0.003), half-time lysis (240 ± 10.00), the total lysis time (485 ± 5.00), lag time in lysis (126 ± 5.77), compared with methylglyoxal at 500 μmol/l (0.104 ± 0.005), (276 ± 5.77), (570 ± 10.00), and (186 ± 5.77), respectively (P < 0.05). Methylglyoxal at 500 μmol/l with aspirin 1 mg/l did not significantly change in either parameter (P > 0.05). Methylglyoxal at 100 μmol/l with aspirin 1 mg/l did not significantly change in either fibrinolysis parameter (P > 0.05), compared with methylglyoxal at 100 μmol/l. Methylglyoxal at 5 μmol/l with aspirin (1, 10, 100 mg/l) changed in all fibrinolysis parameters (P < 0.05), compared with methylglyoxal at 5 μmol/l. The other concentrations were compared in the same way. Aspirin (more than 1 mg/l) had more effect on higher concentrations of methylglyoxal. It increased the velocity of lysis of the clot and shortened clot lysis.