Three species of Echinacea (Echinacea purpurea, Echinacea angustifolia, and Echinacea pallida) are commonly used for medicinal purposes. The phenolic compounds caftaric acid, cichoric acid, echinacoside, cynarin, and chlorogenic acid are among the phytochemical constituents that may be responsible for the purported beneficial effects of the herb. Although methods for the analysis for these compounds have been published, documentation of their validity was inadequate as the accuracy and precision for the detection and quantification of these phenolics was not systematically determined and/or reported. To address this issue, the high-performance liquid chromatography method, originally developed by the Institute for Nutraceutical Advancement (INA), was reviewed, optimized, and validated for the detection and quantification of these phenolic compounds in Echinacea roots and aerial parts.