Thymus magnus, an endemic species, is found in the Republic of Korea. The volatile compounds extracted by SPME from T. magnus were investigated for their chemical composition and electrophysiological response against the Asian tiger mosquito, Aedes albopictus. The volatile compounds of T. magnus as determined by gas chromatography mass spectrometry were γ-terpinene (33.0%), thymol (29.9%), β-bisabolene (8.9%), ρ-cymene (8.3%), α-terpinene (5.0%), myrcene (4.7%), β-caryophyllene (4.0%), α-thujene (2.7%), camphene (1.3%), carvacrol (1.2%), and α-pinene (1.1%). Among these candidates, thymol exhibited complete (100%) repellent activity against female Ae. albopictus, an effect that was confirmed through evaluating the electrophysiological response on the antenna of Ae. albopictus. The effectiveness of a binary 1∶2 mixture of thymol and vanillin (0.05∶0.1 µl per cm²) was found to be significantly more effective than thymol alone for a period of 120 min. In addition, thymol, α-terpinene, and carvacrol showed high larvicidal activity against on the third-stage larvae with LC₅₀ values of 0.9 µl per 100 ml.