Ionizing radiation (IR) has garnered growing attention because of its biological effects on aquatic organisms and humans. Here, we identify the most impacted organs and uncover the molecular mechanisms causing the changes in the context of vertebrate development using single‐cell RNA sequencing. Alterations in cellular composition and biological functions were explored using transcriptomic profiling of zebrafish embryos exposed to 5 Gy. Single‐cell RNA sequencing analyses unveiled notable shifts in the proportions of brain/central nervous system and hatching gland clusters. Although IR exposure led to increased expression of hatching enzymes, a significant but mild delay in hatching was observed following 5 Gy IR exposure. Gene Ontology analysis showed an increased expression of tissue inhibitors of metalloproteinases (TIMPs), known as matrix metalloproteinase inhibitors, which was confirmed via whole‐mount in situ hybridization. Correlation analysis linked TIMPs to transcription factors cebpb and cebpd , which were significantly correlated post‐IR exposure. Although no morphological changes were observed in some organs, including the brain, the study reveals substantial alterations in developing vertebrates. Notably, despite increased hatching enzymes, elevated TIMPs in the hatching gland suggest a regulatory mechanism impacting hatching activity. This research contributes to comprehending the ecological repercussions of IR exposure, emphasizing the importance of safety measures for aquatic ecosystems and overall environmental health.

Ionizing radiation inhibits zebrafish embryo hatching through induction of tissue inhibitors of metalloproteinases (TIMPs) expression