This dataset was collected as part of the MULTICLIM project at the University of Oslo: https://www.mn.uio.no/ibv/english/research/sections/aqua/research-projects/144612/ The data has been published in Ecotoxicology, doi:10.1007/s10646-022-02599-3. The main aim of the study for which the data was collected was to assess how imidacloprid exposure affects a soil community. We addressed this by asking whether 1) imidacloprid exposure affected the soil mesofauna abundance in a concentration- and organism type-related manner, and 2) whether this effect was modulated by the possibility of the mesofauna to migrate into and out of the mesocosms. We conducted a 20-day field experiment with in-situ mesocosms containing intact soil cores exposed to imidacloprid (concentrations of 0, 0.1, 1 and 10 mg/kg dry soil) for understanding community-level responses under field conditions. The dataset contains number of individuals of all soil fauna groups extracted from the samples, however for the published paper we focused on major soil mesofauna groups of springtails and mites, as the chosen extraction method was optimised for these groups.