The Papaveraceae, informally known as the poppy family, are an ethnopharmacologically important family of 44 genera and approximately 760 species of flowering plants. The present work offers a review addressing the detailed chemistry and pharmacology of Argemone mexicana L. regarded as one of the most significant plant species in traditional system of medicine. The plant is used in different parts of the world for the treatment of several ailments including tumors, warts, skin diseases, inflammations, rheumatism, jaundice, leprosy, microbial infections, and malaria. Interestingly, the plant is the source of a diverse kind of chemical constituents although alkaloids are mostly abundant. Beyond pharmaceutical efficacies, certain plant parts also show toxic effects as well. Hence, an up-to-date information on the chemical and pharmacological knowledge on this plant may be helpful to guide researchers anticipating to undertake further investigations in these directions. The present review covers literature up to 2012 and enlists 111 references.