Accidental aconitine poisoning is extremely rare in North America. This report describes the confirmation of a case of accidental aconitine poisoning using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The case involved a 25-year-old man who died suddenly following a recreational outing with friends where he consumed a number of wild berries and plants including one that was later identified as Monkshood (Aconitum napellus). Postmortem blood and urine samples were available for analysis. All routine urine and blood toxicology screens were negative. The LC-MS/MS method allowed sensitive quantification of aconitine, the main toxin in A. napellus, and showed 3.6 and 149 microg/L in blood and urine, respectively. These concentrations were similar to that reported in other aconitine-related deaths. This case illustrates the dangers of consuming unidentified plants, and documents concentrations of aconitine in blood and urine in a fatal case of A. napallus-related poisoning.