The present study was designed to evaluate the effects of pyriproxyfen (PPF) larvicide on ovo-chick neurodevelopment and genotoxicity in embryonic days (EDs) 7 and 14. Fertilized chicken eggs were divided into three groups (G1, G2, and G3) injected with three sub-lethal doses 15, 30, and 45ug PPF/egg, respectively. In both EDs, PPF induced significant levels of mortality, whereas hematoma formation and microcephaly were the common disorders in the head region of all treated groups. The injected groups demonstrated histological neuronal damage in the pallial ventricular zone with distributions of chromatolysis and vacuolated neurons and decreased BDNF expression with restorative expression in ED 7 embryos. The levels of Hsps 70, and 90 of embryos on ED 14 expressed a higher level of gene expression than those of ED 7 with different significant levels.  Additionally, the Tuj1 and Sox10 gene expressions revealed a significant decrease during ED 7 with the highest decrease among the G2 embryos. On the other hand, Tuj1 expression also decreased during ED 14 in G2, but Sox10 gene expression seemed to be upregulated with regenerative ability. In conclusion, ED 7 younger embryos were more affected by PPF and exhibited significant teratogenic brain disorders in developing chick embryos owing to its direct effect on neurogenesis and downregulation of regenerative process proteins.