It has been frequently shown that nanoparticles are able to increase the efficiency of antitumor drugs, decrease their side effects, and control distribution profile of drug molecules. In addition, these particular systems can enhance pharmacokinetics and pharmacodynamics properties of drugs through a physical pathway. This novel strategy can prevent drugs entering systemic circulation, and can confine the access of drugs to a specific target. Various polymeric nanoparticles have been used for the encapsulation of anticancer drugs. This chapter reviews different types of anticancer drugs and engineering techniques for obtaining efficient delivery systems in cancer treatment. It also introduces the salient features of this approach, the hurdles that must be overcome, the hopes associated with it, and practical constraints.