Dicarboximide fungicides, including captafol, captan, cyclohexylthiophthalimide, folpet, and procymidone, represent a distinct category of fungicides. 17β-Hydroxysteroid dehydrogenase 1 (17β-HSD1) catalyzes the conversion of estrone to estradiol in mammals. Yet, the impact of these fungicides on 17β-HSD1 activity remains unknown. In this study, we investigated their inhibition using human placental cytosols, rat and pig ovarian cytosols. Our observations revealed that dicarboximide fungicides significantly inhibited human 17β-HSD1 activity. Among them, captan showed the strongest potency, with its IC