A new method is proposed for determination of TBHQ (tert-butylhydroquinone) individually and in a mixture with BHT (butylated hydroxytoluene) in mineral oil and biodiesel when using linear-sweep voltammetry in combination with a gold disc electrode. Both of these analytes gave rise to the respective anodic peak in the supporting electrolyte based on a mixture of dilute H2SO4 and isopropanol. The samples of mineral oil were extracted using ethanol, and the samples of biodiesel were analyzed without any special sample treatment or separation. The electroanalytical method developed has enabled the determination of antioxidants in model and real samples with satisfactory results and good prospects for practical analysis.