The effect of pesticide contamination on arthropod biomass and diversity in simulated prairie restorations depended on arthropod feeding guild (e.g., predator, herbivore, or pollinator). The pesticides used in this study were the neonicotinoid insecticide clothianidin and the phthalimide fungicide captan. This dataset includes two data files. The first contains information about the study sites ("plots") and pesticide treatments. The second contains information about arthropod biomass and morphospecies richness separated by feeding guild for each month-plot combination. R code in an R Markdown file for the analysis and data presentation in the associated publication is also provided. Detected effects included: predator biomass was 66% lower in plots treated with clothianidin, and this effect persisted across the growing season; the impact on herbivore biomass appeared to be inconsistent, with biomass being 51% lower with clothianidin in June but no detected difference in July or August; herbivore morphospecies richness was 12% lower in plots treated with both clothianidin and captain; pollinators appeared to be unaffected by clothianidin; and pollinator biomass increased by 71% when captan was applied to a plot.