L-abrine and ricinine are two small molecules found respectively in the seeds of Abrus precatorius and Ricinus communis. L-abrine and ricinine are extracted simultaneously with the toxins ricin and abrin from the seeds and are therefore exposure markers for these toxins. We developed and validated a fast and simple method for the simultaneous quantitation of ricinine and L-abrine in plasma and urine by ultra-high performance liquid chromatography coupled with a tandem mass spectrometer (UHPLC LC40 Nexera X3-TQ8060 Shimadzu). A pretreatment step was achieved using solid phase extraction on the Strata®-X 30mg, 1mL cartridge (Phenomenex) before a chromatographic separation on a Luna Omega Polar C18 column (50×2.1mm, 1.6μm; Phenomenex) with a gradient of mobile phase composed of water and acetonitrile, each containing 0.1% formic acid. This method is sensitive (lower limit of quantification at 0.4 and 2ng/mL in plasma and in urine respectively), fast (chromatographic analysis in 5minutes), easier and cheaper than the proteomic analysis of the toxins. It represents an interesting alternative for highlighting an intoxication by ricin or abrin.