Abstract: Sulfoxaflor (Isoclast™ active) is a new insecticide which was first registered in South Korea in 2011 for use in citrus and other crops. Isoclast™ is a systemic insecticide acting as an insect neurotoxin and is a member of a new class of insecticides, the Sulfoximines, which belong to group 4C according to the IRAC MoA Classification. Citrus are among the most consumed fruit worldwide while they also attract many efforts for registration of new pesticides. In the past, abuse and overuse of toxic insecticides caused highly detrimental effects on populations of natural enemies resulting in destruction of natural arthropod balance in citrus ecosystems. Also, pesticide resistance issues arose, which forced citrus farmers to seek pesticides with novel modes of action. What is more, nowadays consumers are demanding natural or eco-friendly pesticides which are supposed to not jeopardize human health and natural balance. To address these issues, the Turkish Ministry of Agriculture brought a new regulation into force requesting proof of safety of any new pesticides in citrus on certain beneficial arthropods. The aim of this study was to evaluate any possible negative effects of sulfoxaflor on the population of Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) Anagyrus pseudococci Girault (Hymenoptera: Encyrtidae), and Chilocorus bipustulatus (L.) (Coleoptera: Coccinellidae) which are amongst the most important beneficials in citrus ecosystems in Turkey. Laboratory bio-assays were conducted and the effect of Isoclast™ was classified according to IOBC standards. In addition, the effect of sulfoxaflor on the parasitoid of mealybugs A. pseudococci was investigated in field trials. Sulfoxaflor proved to be either harmless or slightly harmful to A. swirskii at 0.10, 0.15 and 0.20 ml/l with 17.53, 25.93 and 29.05% corrected mortality, respectively. The highest reduction of offspring, 35.84%, was observed at the dose of 0.20 ml/l. The percentage of Chilocorus bipustulatus larvae which reached the adult stage was 71.96% at the highest dose of 0.20 ml/l, while only 7.5% corrected mortality was observed at 0.10 ml/l. Anagyrus pseudococci was the most sensitive among the three beneficials to Isoclast™. The 0.1 ml/l dose caused 85% corrected mortality of A. pseudococci while the doses of 0.15 ml/l and 0.20 ml/l caused 92.50% and 100% mortality respectively. Since sulfoxaflor showed high contact toxicity to A. pseudococci in the laboratory, evaluation of its effect was investigated further in the field in two citrus orchards at the highest dose (0.2 ml/l). In these field trials sulfoxaflor had practically no any negative effects on the population of A. pseudococci, while the parasitization ratio of mealybugs was found to be higher in trees treated with sulfoxaflor than the untreated and the toxic standard.