This study was aimed to evaluate the effect of diallyl trisulfide (DATS), a major component derived from garlic used to inhibit platelet thromboxane formation, on the pharmacokinetics of dipyridamole. Pharmacokinetic parameters of dipyridamole were determined in rats following intragastric (80 mg/kg suspension or 40 mg/kg solution) or intravenous (3 mg/kg) administration of dipyridamole with coadministration (20 mg/kg) and long-term pretreatment of DATS (10 or 20 mg/kg/day for 15 consecutive days). In addition, everted gut sac models were used to assess transepithelial transport of dipyridamole and the effect of DATS on the intestinal absorption of dipyridamole. After coadministration and long-term pretreatment of DATS, significantly lower $C_{max}$ and $AUC_{0-24h}$ were observed for intragastric administration of dipyridamole, whereas little change was noted after intravenous dipyridamole administration. After adding DATS (10 and $50{mu}g/mL$) in the everted gut sacs, absorption of dipyridamole was remarkably decreased in the ileum and jejunum (p < 0.01). In conclusion, DATS reduced the oral exposure of dipyridamole in rats likely by the modification of the dissolution rate and intestinal absorption of dipyridamole, indicating that combined use of DATS or DATS-containing supplements with dipyridamole may require caution as low plasma concentrations of dipyridamole may lead to a subtherapeutic effect of this agent.