The essential oil (EO) of Sideritis L. has attracted great interest due to its pharmacological activities. At the same time, there is significant variability within the type, related, among other things, to the origin of the raw material. The aim of this work was to study the EO chemical composition of Sideritis scardica Griseb. from Bulgaria and Türkiye. The plant material (air-dried above-ground parts) was purchased from herbal and medical stores in Lublin, Poland. The crushed raw material was used for distillation of the EO. Distillation was performed in a Clevenger apparatus. The EO content was expressed in ml per 100 g of air-dried herb. Analysis of the qualitative and quantitative composition of the obtained EO was performed using gas chromatography coupled with a mass spectrometer (450-GC + 240-MS). The antimicrobial activity of the S. scardica EO was evaluated using the broth microdilution method in accordance with the guidelines of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. We have demonstrated that the chemical composition and biological activity of sideritis EO depend on the origin of the raw material. Our results indicate that S. scardica EO can be considered a promising antimicrobial agent.