Hypoxia-inducible factor-$1{alpha}/{eta}$ (HIF-$1{alpha}/{eta}$) is a heterodimeric transcriptional activator that mediates gene expression in response to hypoxia. HIF-$1{alpha}$ has been noted as an effective therapeutic target for ischemic diseases such as myocardiac infarction, stroke and cancer. By using a yeast two-hybrid system and a random peptide library, we found a 16-mer peptide named F29 that directly interacts with the bHLH-PAS domain of HIF-$1{alpha}$. We found that F29 facilitates the interaction of the HIF-$1{alpha/eta}$ heterodimer with its target DNA sequence, hypoxia-responsive element (HRE). The transient transfection of an F29-expressing plasmid increases the expression of both an HRE-driven luciferase gene and the endogenous HIF-1 target gene, vascular endothelial growth factor (VEGF). Taken together, we conclude that F29 increases the DNA-binding ability of HIF-$1{alpha}$, leading to increased expression of its target gene VEGF. Our results suggest that F29 can be a lead compound that directly targets HIF-$1{alpha}$ and increases its activity.