Technical Abstract: A simple method using microwave-assisted extraction (MWAE) using water as the extraction solvent was developed for the determination of shikimic acid in plant tissue of Brachiaria decumbens Stapf, an important Poaceae forage and weed species widely spread in agricultural and non-agricultural areas throughout the world. High performance liquid chromatography (HPLC) was used for the separation of shikimic acid, and chromatographic data were acquired using photodiode array (PDA) detection. This MWAE technique was successful in recovering shikimic acid from a series of fortified plant tissues at more than 90% efficiency with an interference-free chromatogram. This allowed the use of lower amounts of reagents and organic solvents, reducing use of toxic and/or hazardous chemicals as compared to currently used methodology according to the principles of green chemistry. The method was used to determine the level of endogenous shikimic acid in several species of Brachiária and sugarcane (Saccharum officinarum L.) and on B. decumbens and soybean (Glycine max (L.) Merrill) after treatment with glyphosate [N-(phosphonomethyl)glycine]. The method was sensitive, rapid and reliable in all cases.