A high-performance liquid chromatography-tandem mass spectrometry method (LC-MS/MS) was developed for efficient and confirmatory surveillance of illegal use of estradiol benzoate, even when this substance is used in reproductive control. After cryogenic grinding, estradiol benzoate was extracted from hair with acetonitrile for 24 h on a rocking table. The validation of the method was based on Commission Decision 2002/657/EC using the deuterated analogue of estradiol benzoate as internal standard. Decision limit (0.81 ng/g), detection capability (1.38 ng/g), repeatability CV% (13.7), within in laboratory reproducibility CV% (15.6%), and trueness (99.3%) were calculated. Using the proposed methodology the presence of estradiol benzoate in samples obtained from animals treated to synchronize their estrous cycles can be confirmed.