Objective: The study objective was to determine phenolic components for the quality control (QC) of cultivated Sarcandra glabra (Thunb.) Makino ( S. glabra). Materials and Methods: A sensitive, ultra-high-performance liquid chromatography-tandem mass spectrometric method for the simultaneous determination of 12 phenolic components has been developed. Six caffeoylquinic acids, two caffeoylshikimic acids, and four flavanonol glucosides were selected for the comprehensive analysis of distribution in different parts (root, stem, and leaf). Results: Twelve phenolic components were linear in the concentration range of 0.005–5.0 μg/mL ( R2 > 0.995). The relative standard deviation of intra-day and inter-day precision across three validation runs over the entire concentration range was