Phenolic compounds in aqueous, saponin-rich soapbark tree (Quillaja saponaria Molina) extracts were qualitatively and quantitatively characterized by HPLC-PDA-MS(n) and NMR spectroscopy. (+)-Piscidic acid represented the major constituent (75-87% (w/w) of total phenolics) in all examined extracts (n = 4), ranging from 22.1 ± 0.1 to 34.0 ± 0.2 mg/g of dry matter (DM). Derivatives of p-coumaric acid were present at concentrations from 2.2 to 9.3 mg/g of DM (8.1-20.4% of total phenolics), whereas other phenolic constituents such as glucosyringic acid and vanillic acid derivatives accounted for less than 7% of total phenolics. Generally, all Quillaja extracts showed a highly similar but unique pattern, potentially being useful to authenticate Quillaja extracts in foods, cosmetics, and pharmaceutical formulations. Furthermore, the desired antioxidant activity as well as undesired browning reactions in the final product might also be explained by these phenolic compounds, which were identified for the first time in Q. saponaria extracts.