The brown marmorated stink bug, Halyomorpha halys (Stål 1855) (Hemiptera: Pentatomidae) is an invasive and economically important agricultural and ornamental insect pest nowadays established in many countries. There are numerous methods used for its control. Due to the increased risk of chemical contamination upon the application of synthetic insecticides to control harmful insects, essential oils are gaining increasing attention. In this research, the insecticidal effectiveness of Satureja spicigera (C. Koch) Boiss (Laminaceae) essential oil at 10, 15 and 20 μL/mL doses, and 24, 48, 72 and 96 h against five nymph instars and adults of H. halys was investigated. In addition, the chemical analysis of S. spicigera essential oil was done by GC-MS. The major components of the S. spicigera oil were carvacrol (32.14%), thymol (20.01%), ɣ -terpinene (17.05%), p -cymene (9.08%) and carvacrol methyl ether (5.70%). At the 96th h of the study, the essential oil caused a mortality rate of between 20.1 and 87.5%. The positive control (Nimbecidine ® ) had the highest mortality rates for nymphs (100%) and adults (90.3%). According to the LD 50 and LD 90 values, while the most toxic LD 50 values were recorded as 0.63 and 4.66 μL/mL for the N 1 instar and adults, the lowest LD 90 values were 19.12 and 26.32 μL/mL for the N 5 instar and adults, respectively. In conclusion, results showed that S. spicigera oil had a highly toxic effect against five nymph instars and adults of H. halys .