ABSTRACT Ageratum conyzoides L., belonging to the family Asteraceae, is a tropical plant found in some regions of Africa, Asia and South America. This species is popularly known as billy goat weed, “mentrasto” and “catinga-de-bode” and has a large variety of secondary metabolites and biological activities mentioned in the literature. The objective of this work was to contribute the pharmacobotanical standardization of A. conyzoides. Cross-sections were obtained, by hand, for microscopic characterization of root, stem, petiole and leaf blade; to the leaf blade were still made paradermal and longitudinal sections, scanning electron microscopy analysis and maceration. The analysis showed that secretory structures ducts are evidenced only in the petiole and the leaf blade. The root has parenchymatous medullar region; stem, petiole and leaf blade exhibit striated cuticle. Non-glandular trichomes are present in stem, petiole and leaf blade, while capitate glandular trichomes are present only in the leaf blade and are restricted to the abaxial face. These anatomical features are useful for diagnosis of the species and provide support to their quality control.