3,4-Methylenedioxypyrovalerone (MDPV) is a psychoactive drug with potent stimulant properties and potential for abuse and drug dependency. MDPV was recently classified as a Class I drug by Racing Commissioners International, indicating that it is a banned substance in equine athletes because it lacks therapeutic value in horses. To enforce this ban, a sensitive and fast liquid chromatography-tandem mass spectrometry method was needed. It is for this reason that this method was developed for quantification and confirmation of MDPV in equine plasma. Sample preparation involved liquid-liquid extraction. The analyte was analyzed by a triple-quadrupole linear ion trap mass spectrometer in positive multiple-reaction-monitoring and enhanced product ion scan modes. The method was validated for precision, accuracy, limit of detection (LOD), limit of quantification (LOQ), linearity, stability, extraction recovery, matrix effect, dilution accuracy and selectivity. The extraction recovery was >90%. The linearity range was from 5 to 15,000 pg/mL. LOD and LOQ were 2 and 5 pg/mL, respectively. Intra-day and inter-day accuracies were nearly 100%. The method is suitable for screening, quantification and confirmation of MDPV in equine plasma and has been successfully used to detect and confirm the presence of MDPV in equine plasma obtained post-competition.