Selegiline is used in the treatment of Parkinson's disease (PD), in addition to being used in the treatment of depression. Furthermore, this drug is chemically like amphetamine, which is one of its metabolites. In Brazil, Law 13.103 of the Brazilian Traffic Code requires professional drivers to carry out toxicological tests on their hair for renewal of their driver's license. In this way, this article aims to investigate the presence of amphetamine and methamphetamine in selegiline-claimed users by LC-MS/MS. The developed method was validated according to the European Guidelines for Workplace Drug and Alcohol Testing in Hair. As a result, the methamphetamine was found at the highest concentration in all samples, quantified in the range of 0.393 to 2.855ng.mg⁻¹ among users. The same is true for amphetamine was quantified at concentrations from 0.172 to 0.638ng.mg⁻¹. Despite the low concentrations found, which are directly associated with the time of use, demethyl- and selegiline should be evaluated to confirm the use of this drug. In summary, this paper proves that selegiline users have cross-contamination, and the presence of methamphetamine is indicated in hair toxicological tests also highlights the need to develop sensitive methods in this type of investigation.