An accurate method was developed to analyze trans- and cis-resveratrols in peanut oils using stable isotope dilution ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The linearity ranges for trans- and cis-resveratrols were determined to be 0.2–100 μg/kg, exhibiting satisfactory correlation coefficients (r2trans > 0.9998, r2cis > 0.9996). The limits of detection (LOD) and the limit of quantification (LOQ) were determined to be 0.06 and 0.2 μg/kg, respectively. The recoveries of spiked oil samples ranged from 94.9 to 105.0%, with relative standard deviations (RSDs) less than 6.5% (intra-day) and 7.6% (inter-day). This method was successfully applied to quantify the contents of trans- and cis-resveratrols in commercial peanut oils, ranging from 8.7 to 55.5 μg/kg and 0 to 11.0 μg/kg, respectively. The results demonstrated that the developed method is simple, reliable, and robust for quantifying trans- and cis-resveratrols in peanut oils. Consequently, it exhibits great potential for evaluating adulteration and ensuring the quality control of peanut oils.