Background <p>Selenium nanoparticles (SeNPs) show promising potential as antioxidants in biological applications. Although strobilurins are highly harmful to invertebrates, fish, and amphibians, little research has been conducted on their effects on mammals. The present study is an attempt to determine the positive effects of SeNPs on azoxystrobin (AZO)-induced developmental and testicular abnormalities in rat fetuses.</p> Methods <p>Four equal groups of pregnant rats were utilized: the first group was the control; the second group was given 0.4 mg/kg SeNPs, the third group was given 125 mg/kg AZO, and the fourth group was given 125 mg/kg AZO and then 0.4 mg/kg SeNPs between gestational days 6 to 15.</p> Results <p>Prenatal AZO exposure caused many harmful changes in 20-day old rat fetuses. An evident elevation in the resorption rate and a significant reduction in both body weight and length were observed. Morphological and skeletal anomalies were detected in the AZO group. Moreover, the fetal testis showed significant oxidative stress as well as histopathological and ultrastructural changes. The coadministration of SeNPs decreased the impact of AZO, as it decreased the absorption rate, morphological and endoskeleton anomalies. SeNPs demonstrated strong antioxidant capacity by lowering the lipid peroxidation marker malondialdehyde and increasing antioxidant indicators, which in turn reduced the degree of structural degenerative alterations in the testicular tissue.</p> Conclusions <p>Finally, SeNPs exert a crucial role in mitigating the negative effects of AZO by increasing the antioxidant status.</p>