In this study, a fast and reproducible RRLC-ELSD method for the quantitative analysis of 17 cycloartane glycosides and the aglycone cimigenol in black cohosh rhizomes and dietary supplements has been developed. Separation of the 18 triterpenes was achieved within 16 min using reversed phase material and a gradient elution system consisting of water, acetonitrile and methanol. The method was validated for accuracy (recovery rates from 96.79% to 102.86%), precision (intra-day variation ≤5.98%, inter-day variation ≤3.74%), repeatability (R.S.D. ≤ 6.94%) and sensitivity, with detection limits below 4.0 μg/mL and quantification limits lower than 13.2 μg/mL. Calibration curves were established in the range from 5–1,000 μg/mL, with correlation coefficients higher than 0.998 for all constituents investigated. Peak purity and peak assignment were confirmed by means of RRLC-qTOF-MS and in comparison with reference compounds. Three different MS sources (ESI, APCI and APPI) were compared for their ionisation potential regarding cycloartane derivatives. One of the isolated black cohosh constituents, 24-O-acetylhydroshengmanol-3-O-α-l-arabinopyranoside, could be identified as new natural compound.