Lung cancer remains one of the leading causes of cancer-related mortality worldwide, with non-small cell lung cancer (NSCLC) constituting the most common subtype. However, many patients with NSCLC fail to achieve adequate responses to chemotherapy, leading to limited clinical benefit. Hypoxia-inducible factor-1α (HIF-1α) is a critical driver of drug resistance in NSCLC, yet no clinically approved targeted inhibitor has been identified to date. To address this therapeutic gap, we developed ACF-01, a novel flavonoid-based small molecule designed to activate prolyl hydroxylase domain protein 2 (PHD2), the key regulator of HIF-1α stability. ACF-01 directly engaged PHD2, thereby promoting HIF-1α hydroxylation and von Hippel–Lindau (pVHL)-mediated proteasomal degradation. Co-treatment with the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor osimertinib further amplified this effect, producing a more pronounced reduction in HIF-1α protein levels. Accordingly, combined ACF-01 and osimertinib treatment downregulated HIF-1α–regulated glycolytic and angiogenic markers while substantially increasing apoptosis and cell-cycle arrest in NSCLC cells. In vivo, ACF-01 markedly potentiated the antitumor efficacy of osimertinib in nude mice bearing HCC827 xenografts. Pharmacokinetic and toxicological profiling revealed that ACF-01 exhibited high metabolic stability, minimal cytochrome P450 interaction, and an excellent safety margin without cardiotoxicity, genotoxicity, or systemic toxicity. These findings demonstrate that pharmacologic PHD2 activation destabilizes HIF-1α and sensitizes NSCLC to osimertinib, establishing ACF-01 as a rational synergistic partner for EGFR-targeted therapy.