Aim:To identify and screen the phytochemicals of medicinal plants with anti-diarrhea potential in Lagos State, Nigeria. Place and Duration of the Study: Ethnobotanical survey and phytochemical screenings of plants used in traditional medicine for the treatment of diarrhea in Nigeria were carried out between April and November, 2014. Methodology: Ethnobotanical survey of medicinal plants used for the treatment of diarrhea in Lagos State, Nigeria was carried out using oral interviews (without questionnaire) method to gather information from herb sellers in major herbal markets in Lagos State. The qualitative phytochemical screenings of the identified medicinal plants was carried out using standard screening procedures. Results: Twenty-five plant species belonging to 16 families were identified. The families Asteraceae, Lamiaceae and Combretaceae have the highest number of plant species followed by the family Fabaceae. Aristolochia albida, Parinari curatellifolia, Acanthospermum hispidum, Phyllantus amarus and Gongronema latifolium were the most frequently mentioned and highly 2 recommended of all the species. The plant parts used for the treatment are the leaves, bark and roots which were prepared by infusion, decoction or taken in powdered form. Majority of the plants are taken orally. The phytochemical screening revealed the presence of alkaloids, tannins, flavonoids, cardiac glycoside, anthraquinones and phlobatannins.