An efficient and targeted treatment for tumor cells is demonstrated. This targeting is based upon the strong affinity between hydroxyl-functional groups on graphene and acidic tumors. The hydroxylated graphene (GOH) with a unique 2D architecture further improve the targeting capacity of the system via an enhanced permeability and retention (EPR) process. Polyethylene glycol (PEG) was employed for better biocompatibility and the antitumor drug doxorubicin (DOX) was then incorporated. These additions created a biocompatible system with a superior pH-dependent drug release property. Its proficiency was due to its ability to pass through cell membranes via a process of endocytosis and exocytosis. The results from a Transwell co-culture system discovered that the PEG-GOH-DOX system had a large impact on tumor cell viability (less than 10% survived after treatment) and little influence on normal cells (more than 80% survived). An in vitro 3D tumor model study demonstrated that the size of the PEG-GOH-DOX treated tumor was 50% less than that of the pristine DOX treated tumor. In vivo data indicated that the PEG-GOH-DOX system was able to inhibit the size of tumors by a factor of 6.5 when compared to the untreated tumors.