Small interfering RNAs (siRNAs) are a rapidly emerging class of innovative nucleic acid medicines for the treatment of diseases such as cancer. However, significant hurdles hamper their clinical application, including poor cellular uptake, instability under physiological conditions, off-target effects, and possible immunogenicity. The development of suitable delivery systems that protect and efficiently transport siRNA to targeted cells has been pursued. Nanoparticle-based vectors have been widely investigated as potential candidates for effective siRNA delivery. Among the different nanoparticles, polymeric micelles, which are self-assembled nanoparticles composed of amphiphilic materials with a core-shell structure, have attracted great attention in recent years. Polymeric micelles in the range of several tens to hundreds of nanometers can be prepared, regulated, and modified relatively easily. The outer hydrophilic segments can prolong the in vivo lifetime of siRNA to achieve effective accumulation in tumors and can also be modified with cationic charges that interact electrostatically with siRNA and be introduced with different moieties to target specific cells. The inner cores can improve the stability of micelles and serve as payloads for hydrophobic drugs. Here, the barriers impeding siRNA delivery, the different polymeric micelles of siRNA developed to date, their gene silencing or therapeutic activity, and advanced applications for the co-delivery of drugs and siRNA by these delivery systems are reviewed.