Various types of nanoparticles, such as liposomes, polymeric micelles, dendrimers, superparamagnetic iron oxide crystals, and colloidal gold, have been employed in targeted therapies for cancer. Both passive and active targeting strategies can be utilized for nano-drug delivery. Passive targeting is based on the enhanced permeability and retention (EPR) effect of the vasculature surrounding tumors. Active targeting relies on ligand-directed binding of nanoparticles to receptors expressed by tumor cells. Release of loaded drugs from nanoparticles may be controlled in response to changes in environmental condition such as temperature and pH. Biodistribution profiles and anticancer efficacy of nano-drugs in vivo would be different depending upon their size, surface charge, PEGylation and other biophysical properties. This review focuses on the recent development of nanoparticles for tumor targeted therapies, including physicochemical properties, tumor targeting, control of drug release, pharmacokinetics, anticancer efficacy and safety. Future perspectives are discussed as well.