This article describes a fast and simple methodology for the extraction and determination of organic acids in tissues and root exudates of maize, lupin, and chickpea by LC/MS/MS. Its main advantage is that it does not require sample prepurification before HPLC analysis or sample derivatization to improve sensibility. The results obtained showed good precision and accuracy, a recovery close to 100%, and no significant matrix effect. Moreover, the sensibility of the method is in general better than that of previously described methodologies, with detection limits between 15 and 900 pg injected.