Nanosize plasma proteins could be used as a biomimetic drug delivery system (DDS) for cancer treatment when loaded with anticancer drugs based on the fact that plasma proteins can serve as a source of nutrients for cancer cells. This prompted us to investigate the potential of α1-acid glycoprotein (AGP) for this role because it is a nanosize plasma protein and binds a variety of anticancer agents. Pharmacokinetic analyses indicated that AGP is distributed more extensively in tumor tissue than human serum albumin, which was already established as a cancer DDS carrier. AGP is possibly being incorporated into tumor cells via endocytosis pathways. Moreover, a synthetic AGP-derived peptide which possesses a high ability to form an α-helix, as deduced from the primary structure of AGP, was also taken up by the tumor cells. AGP loaded with anticancer agents, such as paclitaxel or nitric oxide, efficiently induced tumor cell death. These results suggest that AGP has the potential to be a novel DDS carrier for anticancer agents.