A validated analytical method is reported for the analysis of narirutin and hesperidin in Zhi Ke (Citrus aurantium L.) in the form of the dried raw herb and of the commercially prepared dried aqueous extract. The samples were extracted by sonication in methanol and the extract was analyzed by liquid chromatography-photodiode array (PDA) detection with identity confirmation by negative electrospray ionization-tandem mass spectrometry (MS). A C18 column was used with a methanolwater gradient mobile phase. Narirutin and hesperidin were quantified at 284 nm using the PDA detector. Using the MS detector, the narirutin precursor ion with m/z 579 produced daughter ions with m/z 271 and 151. For hesperidin, the precursor ion with m/z 609 produced the m/z 301, 285, and 164 ions. The amounts of narirutin and hesperidin found in the certified raw herb were 14.2 and 147.9 mg/g, respectively, and in the dried aqueous extract the amounts were 9.2 and 8.6 mg/g, respectively. For the raw herb, the average recovery across the three spike levels (50, 100, and 150) for narirutin and hesperidin were 110.7 and 94.5, respectively. For the dried aqueous extract, the average recovery across the three spike levels for narirutin and hesperidin were 85.8 and 98.9, respectively.