A new species of Agistemus, A. amazonicus Paktinat-Saeij, Bagheri & Noronha sp. nov. is described based on females collected from leaves of Cupuaçu (Cupuassu) trees (Theobroma grandiflorum (Willd. Ex Spreng.) Schumann), in the Pará state, Brazil. Also, a key to the American Agistemus species is provided.
