Updated project metadata. Hypoxia is a hallmark of solid tumors. Mitochondria play essential roles in cellular adaptation to hypoxia, but the underlying mechanisms are not fully understood. Through mitochondrial proteomic profiling, we find that the prolyl hydroxylase EglN1 accumulates on mitochondria under hypoxia. EglN1 substrate binding region 23 loop is responsible for its mitochondrial translocation and contributes to tumor growth. Furthermore, we identify AMPK as an EglN1 substrate on mitochondria. The EglN1-AMPK interaction is essential for their mutual mitochondrial translocation. EglN1 prolyl-hydroxylates AMPK under normoxia, then they rapidly dissociate following prolyl-hydroxylation, leading to their immediate release from mitochondria. While hypoxia results in constant EglN1-AMPK interaction and accumulation on mitochondria, leading to the formation of CaMKK2-EglN1-AMPK complex to activate AMPK phosphorylation, consequently ensuring metabolic homeostasis and tumor growth. Our findings demonstrate EglN1 as an oxygen-sensitive metabolic checkpoint signaling hypoxic stress to mitochondria through its 23 loop, revealing a therapeutic target for solid tumors.