The essential oils (EOs) of Telekia speciosa, a perennial plant native to southeastern Europe and Asia Minor, were analyzed for their composition and biological properties. T. speciosa is an invasive plant in Poland; however, its beauty prompts gardeners to cultivate the plants. T. speciosa serves as a valuable source of nectar and pollen for honey bees. Our results revealed more than 150 compounds in the flower, leaf, and root EOs. Major constituents found in the essential oils from the roots included isoalantolacton (46.2%) and from the flowers nerol (11.9%), while from the leaves, they included (E)-nerolidol (10.1%). T. speciosa flower EO showed significant cytotoxicity against A375 cells, with IC50 values of 7.2, 5.1, and 3.4 μg/mL referring to 24, 48, and 72 h, respectively, indicating its potential as a natural cytotoxic agent. The antimicrobial activity of the essential oils against Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 25922 was also investigated. The essential oils from the flowers and leaves of T. speciosa demonstrated higher inhibitory activity against S. aureus (MIC: 5.9–7.8 μL/mL) and E. coli (MIC: 7.8–11.7 μL/mL) than the essential oil isolated from the roots of the plant (MICs 31.3 and 62.5 μL/mL against S. aureus and E. coli, respectively).