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Pesticides have reached aquatic ecosystems and have caused numerous impacts on organisms. The present study aimed to assess the sensitivity of Daphnia similis Straus 1820 and Pseudokirchneriella subcapitata (Korshikov) F.Hindák to three commercial pesticides with different active ingredients: Siptran 500SC® (atrazine), Dimilin® (diflubenzuron), and Aproach Prima® (picoxystrobin + cyproconazole). For this purpose, we performed acute toxicity tests on these organisms. The compound most toxic to D. similis was the insecticide Dimilin® (toxic up to 5 μg/L of the active ingredient), followed by the fungicide Aproach Prima® (48h-EC50: 47.33 μg of the active ingredients/L) and the herbicide Siptran 500SC® (48h-EC50: 534.69 mg of the active ingredient/L). In contrast, Siptran 500SC® was the most toxic compound (96h-IC50: 52.61 μg/L) to P. subcapitata, followed by Aproach Prima® (96h-IC50: 164.73 μg/L) and Dimilin® (non-toxic up to 1 g/L). The toxicity of the fungicide to algae and microcrustaceans demonstrates that compounds developed for certain organisms are able to affect others, indicating the relevance of conducting ecotoxicological tests on different organisms.