Hypoxia-inducible factor 1 (HIF-1) mediates a metabolic switch that blocks the conversion of pyruvate to acetyl-CoA in cancer cells. Here, we report that HIF-1α also inhibits fatty acid β-oxidation (FAO), another major source of acetyl-CoA. We identified a PGC-1β-mediated pathway by which HIF-1 inhibits the medium- and long-chain acyl-CoA dehydrogenases (MCAD and LCAD), resulting in decreased reactive oxygen species levels and enhanced proliferation. Surprisingly, we further uncovered that blocking LCAD, but not MCAD, blunts PTEN expression and dramatically affects tumor growth in vivo. Analysis of 158 liver cancer samples showed that decreased LCAD expression predicts patient mortality. Altogether, we have identified a previously unappreciated mechanism by which HIF-1 suppresses FAO to facilitate cancer progression.