Cephalaria species in Turkey known as "Pelemir" and they have many different biological activities due to their wide range of chemical content. The main goal of this study is determine the flavonoids and phenolic acids in Cephalaria species using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). This method was developed for quantitation of reported compounds using reverse phase Fortis C18 (150 x 3 mm x 5 mu m) column with a gradient of 0.1% formic acid solution (A) in water and (B) in methanol in ESI mode. The recoveries of developed method were obtained in the range of 90.4-109.4%. Limit of detection (LOD) and limit of quantification (LOQ) values were calculated in the range of 0.3-25.2 ppb and 3.0-102.3 ppb for the reported compounds. Uncertainty evaluations of all compounds were reported. Twenty-five flavonoids, five simple phenolics, two triterpenoids, one iridoid and vitamin C successfully identified and quantified for nineteen Cephalaria species. The main flavonoids in the studied species were determined as cyanidin-3-O-glucoside, luteolin-7-O-glucoside, kaempherol-3-O-glucoside, hyperoside, hesperidin, luteolin and quercetin while salicylic and caffeic acids were detected as major phenolic acids in the analyzed samples. This is the first full characterization study for nineteen Cephalaria species via HPLC-MS/MS. (C) 2019 Elsevier B.V. All rights reserved.