Rising numbers of psychoactive tryptamine derivatives have become available on the drug market over the last decade, making these naturally occurring or synthetically manufactured compounds highly relevant for forensic analysis. One of these compounds is 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), a constituent of the dried poison of Incilius alvarius (Colorado River toad) which has a history of ritual and/or recreational use. Still, comprehensive and validated qualitative as well as quantitative analytical data on the psychoactive components of this poison are scarce. In this study samples of the poison of Incilius alvarius were collected from live toads in the Sonoran Desert, Arizona (USA) and analyzed with a set of complementary methods. Acetone/water (70/30, v/v) proved to be the solvent of choice for the extraction of tryptamine derivatives. Trace compounds were enriched and overload with 5-MeO-DMT was prevented by chromatographic separation of 5-MeO-DMT prior to qualitative analysis. The method for quantification was validated. Applying attenuated total reflection-Fourier transform infrared spectroscopy to samples of the poison, 5-MeO-DMT was identified as the main tryptamine by comparison to the reference spectrum. The combined evaluation of analytical data gained from gas chromatography-mass spectrometry (GC-MS), liquid chromatography-quadrupole time-of-flight high resolution MS (HPLC-qToF-HRMS), and HPLC-MS/MS confirmed the presence of 5-MeO-DMT, 5-MeO-N-methyltryptamine, 5-MeO-tryptamine, 5-MeO-tryptophol, 2-(5-methoxy-1H-indol-3-yl)-acetic-acid (5-MIAA), 5-HO-N-methyltryptamine, bufotenin, DMT, and tryptophan. For the first time, 5-MeO-tryptamine and two positional isomers of indole-substituted HO-MeO-DMT were detected in the poison of Incilius alvarius. The tryptamine present in the highest concentrations was 5-MeO-DMT (mean ± standard deviation: 410,000 ± 30,000 µg/g). Mean concentrations of 5-MeO-tryptamine (490 ± 260 µg/g), 5-HO-N-methyltryptamine (270 ± 120 µg/g), bufotenin (2,800 ± 1,900 µg/g), and DMT (250 ± 80 µg/g), showed a relatively high variability between individual samples. The comprehensive analytical reference data of Incilius alvarius poison presented here might prove useful for forensic chemists.