We assessed the risk factors of neonatal seizures and their influences on neurodevelopment in very-low-birth-weight infants (VLBWIs). 16,279 VLBWIs born in 2013-2020 were included using Korean Neonatal Network data to assess the risk factors of neonatal seizures. 7,599 VLBWIs born in 2013-2018 and followed up at 18-24 months corrected age were included to assess the influence of seizures on mortality and any neurodevelopmental impairment (NDI) including blindness, deafness, cerebral palsy (CP), and mental and motor NDI based on Bayley test (NDI-Bayley). We also compared clinical factors between no NDI and any NDI groups after neonatal seizures. 1,430 infants (8.8%) had neonatal seizures. Significant risk factors for neonatal seizures were lower GA, male gender, congenital anomaly, small for GA, delivery room resuscitation, maternal chorioamnionitis, surfactant use, hypotension, severe intraventricular hemorrhage (IVH), post-hemorrhagic hydrocephalus, sepsis, meningitis, and necrotizing enterocolitis (NEC). In the subgroup analysis, lower GA and male gender increased the risk of seizures only in GA < 28 weeks group. Neonatal seizures increased the risk of deafness, CP, and NDI-Bayley. Significant risk factors for any NDI after seizures were severe IVH and NEC. Providing the best treatments for morbidities of VLBWIs in NICUs could prevent neonatal seizures and NDI after seizures.