Spiropidion is a new active ingredient developed by Syngenta. It belongs to the group of acetyl-CoA carboxylase inhibitors (group 23) and to the subgroup of tetronic and tetramic acid derivatives, which act as growth and development regulators of insects and mites. They inhibit acetyl-coenzyme A carboxylase, an important participant in the first part of lipid biosynthesis. An application for registration of this insecticide in the European Union will be submitted next year. It is expected that immediately after registration in the EU, it will also be marketed in Croatia. In order to better understand the effect of this insecticide on pests and natural enemies, a trial conducted in 2019 determined the efficacy on cotton aphids on peppers and the side effect on the predatory mite Ambliseius swirskii. The experiment was conducted in two greenhouses: in greenhouse I, the predatory mite A. swirskii was released and aphids were treated with spiropidion at a dose of 80 and 40 g at / ha, while in greenhouse II no mite was released and only the full dose (80 g at / ha) of spiropidion was applied. Due to the low number of mites in the experiment, it was not possible to fully confirm the claims in the literature about the absence of a negative effect of spiropidion on predatory mites. The insecticide tested is highly effective against cotton aphids (infesting plants in our experiment) at both dosages applied (40 and 80 g a.t./ha) and should definitely be recommended at a lower dosage for practical use. Satisfactory efficacy was observed at least two weeks after treatment. When marketed in the Republic of Croatia, spiropidion will be a valuable agent for aphid control in the production of peppers in a protected area, as it has no negative effects on predatory mites and the results of numerous studies show a favorable ecotoxicological profile.