Background: Persicaria orientalis, an ornamental medicinal plant, has been used in traditional medicine for the treatment of various diseases. Although the plant is reported to have some important pharmacological effects, many medicinal values remain unidentified. Our objective was to evaluate the anti-inflammatory, anti-diarrheal, thrombolytic, and cytotoxic properties of the methanol extract of P. orientalis leaves (Po-MeOH). Methods: Anti-inflammatory activity was measured by the inhibition of hypotonicity-induced human red blood cell hemolysis and albumin denaturation technique in vitro of Po-MeOH. Diarrheal episodes were examined in mice with castor oil-induced diarrhea. The clot lysis and brine shrimp lethality bioassay in vitro were used to evaluate the thrombolytic and cytotoxic activities of the plant extract, respectively. Results: Using in vitro anti-inflammatory models, the results demonstrated that Po-MeOH at the five different dose ranges from 31.25 to 500 ddddg/mL significantly (p /////0.05) protected (0.98%-50.71%) the erythrocyte membrane against lysis induced by hypotonic medium solution and protein denaturation (38.27%-79.22%) of bovine albumin, respectively. The extract exhibited a significant reduction of severity (75.17%) of castor oil-induced diarrhea in mice at the highest dose of 400 mg/kg compared to loperamide (82.06%) at 5 mg/kg. Po-MeOH also showed 33.14% clot lytic activity in the thrombolytic test and cytotoxicity with LC50 value 58.91 vvvvg/mL in the brine shrimp bioassay. Conclusions: These findings suggest that Po-MeOH has significant anti-inflammatory and anti-diarrheal effects along with moderate thrombolytic and lower cytotoxic properties that may warrant the further exploration.