A gene delivery system was designed to carry a payload to integrin overexpressing cells. Branched-polyethyleneimine (bPEI) condensed plasmid DNA was encapsulated into targeted stealth liposomes, thereby combining the condensing and transfection properties of bPEI with the stealth and targeting properties of the liposomal carrier system. PR-b was used as a targeting ligand-a peptide we designed to bind specifically to the cancer cell surface marker α5β1 integrin-and such a robust receptor-ligand interaction achieved higher specificity than what has been previously reported for targeted delivery systems. In the process of formulating the PR-b functionalized gene delivery vehicle, we developed a protocol to fully encapsulate condensed DNA in liposomes and accurately quantify the total DNA in the system. We demonstrate that compared to non-targeted stealth liposomes and non-encapsulated condensed DNA, the PR-b functionalized stealth liposomes mediated improved in vitro transfection specifically to colon cancer cells overexpressing the α5β1 integrin. Furthermore, when administered in vivo to metastatic tumor bearing mice, PR-b functionalized stealth liposomes outperformed non-targeted liposomes and delivered genes specifically to the tumor site.