A series of 2-(arylmethylthio)-3-phenylquinazolin-4-one derivatives have been synthesized and their antiplatelet aggregation activities were assessed against ADP and arachidonic acid-induced platelet aggregation in human plasma. Among the tested thioethers, derivative 2, 3, 5 and 16 were the most potent compounds with satisfactory $IC_{50}$ for inhibition of platelet aggregation induced by ADP. Analysis of global physicochemical parameters shows some correlations between activities and molecular volume and also surface area of the studied derivatives.