As the most commercial polymer, the polyethylene nanoparticle (PE-NP) has been discharged into the environment and poses potential risks to organisms. However, the possible reproductive toxicity of PE-NP and underlying mechanisms remain largely unknown. In this study, Caenorhabditis elegans was employed as the animal model to effects of PE-NP (100&#
xa0;nm) and their leachates on reproduction and underlying mechanisms. Nematodes were exposed to PE-NP at 0.1-100&#
xa0;&#
x3bc;g/L from L1-larvae to adult day 1 (approximately 4.5&#
xa0;days). Both brood size and number of fertilized eggs in uterus were decreased by 10 and 100&#
xa0;&#
x3bc;g/L PE-NP, but could not be affected by their leachates. In addition, number of mitotic cells, length, and area of gonad were reduced by 10 and 100&#
xa0;&#
x3bc;g/L PE-NP, but were not altered by their leachates. Accompanied with alteration in expressions of genes (
egl-1,
ced-9,
ced-4, and
ced-3) governing cell apoptosis, germline apoptosis was enhanced by PE-NP. Meanwhile, DNA damage was involved in the enhancement germline apoptosis after PE-NP exposure. PE-NP further increased expression of
nhr-14 encoding estrogenic hormone receptor, and RNAi of
nhr-14 suppressed PE-NP reproductive toxicity. Moreover, RNAi of
nhr-14 decreased expression of
egl-1,
ced-4,
ced-3, and
mrt-2 in PE-NP exposed nematodes. Therefore, exposure to PE-NPs rather than in their leachates potentially caused reproductive toxicity by activating both estrogenic hormone receptor NHR-14 and DNA damage checkpoints (CLK-2, HUS-1, and MRT-2) in nematodes. These findings provide important insights into the exposure risk of PE-NPs on reproduction of environmental organisms.