Based on the traditional folk use, the anti-diarrheal activity of the methanolic extract of Achillea millefolium L. (AM) leaves was evaluated on castor oil-induced diarrhoea and assessment of gastrointestinal propulsion of charcoal meal in rats. Achillea millefolium L. commonly known as yarrow belonging to the family Asteraceae, is an ancient traditional herb native to Europe and is used to treat wounds, hepatic disorders, gastrointestinal disorders, spasmodic diseases, headaches, pain, inflammation and diarrhoea. The three doses of Achillea millefolium L. methanolic extract has been selected (150 mg/kg, 300 mg/kg and 450 mg/kg). Among three dosages of AM leaves, the two dosages (300 mg/kg-IIIb and 450 mg/kg IIIc) showed a significant reduction in various parameters like distance travelled (IIIb-25±1.679 cm; IIIc-17±2.534 cm) and % average travelled (IIIb-47.16; IIIc-32.69) travelled in charcoal meal model when compared to control group. Phytochemical screening of the plant extract revealed the presence of flavonoids, tannins, steroids and terpenes. Results showed that the methanolic extract of Achillea millefolium Leaves possess anti-diarrhoeal activity possibly mediated by inhibiting the intestinal motility, hydroelectrolyte secretion and by making intestinal mucosa more resistant to chemical alteration and hence reduce secretions.