Ambrosia cumanesis K (Asteraceae), known as Altamisa, is an aromatic species widely distributed throughout the country. Its use is associated with the treatment of kidney, anti-inflammatory, antiparasitic and laxative disorders. The chemical characterization of the aqueous and ethanolic extracts of the leaves of A. cumanesis K. was carried out, as well as of its essential oil, in order to evaluate its biological activity. Phytochemical screening tests were carried out to identify secondary metabolites, chromatographic methods were used for the purification of plant extracts and the identification of the main compounds was carried out by IR and NMR spectroscopy, and by CG-MS for the essential oil. The chemical analysis of the ethanolic extracts of the fresh leaves of Ambrosia cumanensis Kunth has led to the identification of alkaloids, terpenes and flavonoids as the major secondary metabolites. The extraction and purification of the extracts led to the isolation of three (3) known compounds, psilostachyn A, psilostachyn C and camphor. The analysis of the chemical composition of the essential oil of this plant has led to the identification of 25 compounds and the possible correlation between the composition variability and the seasonality. The microbiological activity of the ethanolic extracts and the essential oil was evaluated by inhibition halo, showing selective antimicrobial activity for the essential oil. This is the first report of chemical studies on Ambrosia cumanensis Kunth in Panama.