In this work, a fast and low-cost voltammetric methodology for determination of carlina oxide in plant extracts was developed. The best results were obtained using a boron-doped diamond electrode (BDDE). The voltammetric measurements of carlina oxide were performed in a 0.1 mol/L solution of sulphuric acid. After 30 s of stirring the solution, differential pulse voltammograms (DPVs) were recorded from 0.5 to 1.8 V. The amplitude was 75 mV and the scan rate was 175 mV/s. Measurements were recorded in non-deaerated solutions. The background current was subtracted from each registered voltammogram; then they were cut from 0.5 to 1.5 V. The detection and quantification limits were 0.28 and 0.93 μg/L, respectively, and repeatability expressed as the relative standard deviation of 0.1 mg/L of carlina oxide was 1.9% (n = 5). The results were compared with those obtained using gas chromatography with a flame ionization detector and high performance liquid chromatography with a photodiode array detector.