Technical Abstract: Insecticidal seed treatments are becoming a pervasive presence on soybeans in North America, and several recent studies question their efficacy. Here, we examine the effects of two neonicotinoid insecticidal seed treatments on insect populations (pest and natural enemies) in SD soybeans over two years. Moreover, we conducted laboratory experiments to determine the duration that seed treatments remained effective against the soybean aphid, and how thiamethoxam affected survival one of the aphid’s predators, Orius insidiosus (Hemiptera: Anthocoridae) on soybean. Soybean aphids, thrips, and grasshopper populations were unaffected by the insecticidal seed treatments in the field. The laboratory trial revealed that all bioactivity of the seed treatments against soybean aphids was gone by June 30th, prior to aphid populations damaging the crop. Bean leaf beetles, a sporadic pest in our area, was reduced by the seed treatments. But there were no yield benefits of insecticidal seed treatments for producers. Natural enemy communities were significantly reduced by thiamethoxam seed treatments relative to the untreated control, particularly populations of Chrysoperla and Nabis americoferus. In the laboratory, rearing O. insidiosus on soybean plants treated with thiamethoxam resulted in higher mortality for both the nymphs and the adult stage. Offering the predator insect prey on the thiamethoxam-treated plants improved survival of the adult stage, but not the nymphal stage. This work confirms that insecticidal seed treatments offer little benefit to soybean producers of our region, and adds to the discussion by suggesting that generalist predators are adversely affected by the insecticides.