Tumor targeted therapy has brought a new hope to the cancer patients. With the recent advances in nanotechnology and growing knowledge on unique cancer biomarkers, it is now possible to manipulate the surface architecture of polymeric nanoscale delivery systems with targeting moieties, such as antibodies, antibody fragments, specific molecules, small peptides, RNA aptamers etc. to target specific receptors and antigens present exclusively or overexpressed on the tumor cell surface or on the tumor endothelial cell surface. These modified polymeric nanoparticles deliver the loaded chemotherapeutics preferentially to the tumor tissue and not to the healthy tissue. This ensures highly targeted treatment without severe side effects which are normally experienced by the cancer patients in case of conventional chemotherapy. Such specifically constructed polymeric nanocarriers with improved tumor targeting profile are now regarded as engineered polymeric nanoparticles, which have become one of the prime areas of drug delivery research in recent times. This review describes specific approaches used in recent years to construct engineered polymeric nanoparticles, their emerging potential for cancer therapy and recent advances in tumor targeting. An equal attention has been devoted to the fundamental problems encountered in practical fields which limit their clinical use and industrial production.