The emergence of antibiotic-resistant bacteria has intensified the search for novel antidiarrheal drug. Plant-derived extracts offer promising alternatives due to their ability to modulate gut motility and enhance water absorption. The leaves of Leucas deflexa Hook.f., a plant native to Ethiopia, have been traditionally utilized in the treatment of diarrheal diseases. Nonetheless, its traditional application has yet to be scientifically confirmed. Hence, the aim of the present study was to evaluate antidiarrheal activity of the crude extract and fractions of the leaf of Leucas deflexa Hook.f (Lamiaceae). Healthy Swiss albino mice were randomly divided into five groups per experimental model: castor oil-induced diarrhea, gastrointestinal motility, and anti-enteropooling assays. The control group received distilled water (10 ml/kg), while the positive control was treated with loperamide (3 mg/kg). The remaining groups were administered various dosages (LD100, LD200, and LD400 mg/kg) of a hydroalcoholic extract or its fractions from Leucas deflexa Hook.f. The crude extract and chloroform fraction substantially (P < 0.001) delayed the onset of diarrhea, reduced fecal frequency, and decreased total fecal weight at all administered doses compared to the negative control. The butanol and aqueous fractions exhibited a substantial antidiarrheal effect at doses of 200 mg/kg and 400 mg/kg, respectively. All treatments, including the crude extract, chloroform, butanol, and aqueous fractions, substantially (P < 0.001) reduced the volume and weight of intestinal contents at various doses. Additionally, the chloroform, aqueous fraction, and crude extract at doses of 100, 200, and 400 mg/kg substantially inhibited gastrointestinal motility compared to the negative control. The results of this study corroborate the traditional use of Leucas deflexa leaves in the treatment of diarrhea. These findings give a scientific justification for further exploration of the underlying mechanisms and potential therapeutic applications of this plant extract.