Circular RNAs (circRNAs) are non-coding RNAs with covalently closed loop structures that participate in various biological processes. However, the functions of many circRNAs remain unclear. Endothelial cell dysfunction, which involves abnormal ferroptosis, a unique form of regulated cell death, is a characteristic of various diseases. However, the mechanisms governing ferroptosis in endothelial cells are not fully understood. Here, we investigated the impact of a novel circRNA, circ-DAPK1, on ferroptosis in human umbilical vein endothelial cells (HUVECs) under high-glucose conditions. Our data showed that high-glucose conditions upregulate circ-DAPK1 expression in HUVECs. Overexpression of circ-DAPK1 induced ferroptosis in HUVECs, whereas depletion of circ-DAPK1 mitigated the ferroptosis triggered by high-glucose treatment. Inhibition of ferroptosis reversed the decrease in cell viability induced by high glucose or circ-DAPK1 overexpression. Using RNA immunoprecipitation analyses, we identified several ferroptosis-regulating proteins, including NAD(P)H dehydrogenase [quinone] 1 (NQO1) and insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2). Mechanistically, circ-DAPK1 interacts with NQO1, enhancing its ubiquitination and accelerating its degradation. NQO1 overexpression partially rescues HUVECs from high-glucose-induced ferroptosis. We also found that IGF2BP2 binds to the m