Purpose of ReviewThere is an urgent need to develop novel drug delivery systems due to constraints associated with existing cancer therapies.Recent FindingsThe tumor microenvironment compared to normal cells is distinct, and this difference in the microenvironment of cancer cells is utilized as stimuli in anticancer therapy. Polymer is one of the most potential drug delivery candidates in this regard. Smart polymers, also known as stimuli-sensitive polymers, are employed to transport a variety of medications, including anticancer treatments. Polymeric nanoparticles constitute multiple architectures, such as vesicles, micelles, nanospheres, nanogel, core-shell geometries, etc., synthesized from responsive polymers exhibit a remarkable role in drug delivery. Alongside the drug delivery application, smart polymers can also be employed as biosensors, catalysis, separation membrane, and artificial scaffolds.SummaryDue to the high amount of glutathione (GSH) found in some types of malignancies, polymers susceptible to redox reactions are frequently developed to react with internal microenvironmental stimuli. This review discusses the reduction-responsive polymers, especially for tumor targeting applications, and the diverse set of morphologies in polymeric nanoparticles employed for the delivery techniques.