Mycn, a MYC gene family member, is implicated in both carcinogenesis through amplification and Feingold syndrome through its deficiency. Previous studies have indicated that increased Mycn expression enhances vascularization in human neuroblastomas, yet its precise role in vascular development remains elusive. In this study, we utilized single-cell RNA-seq and live imaging analyses to confirm that mycn is expressed during zebrafish vasculogenesis. We investigated vascular development in zebrafish using a genetically engineered mycn mutation. Our findings reveal that mycn-deficient zebrafish exhibit reduced intersegmental vessels and malformed subintestinal vessels, primarily due to decreased cell proliferation in vascular cells. Importantly, we discovered that activation of PI3K signaling significantly ameliorates these vascular abnormalities.