Circulating tumor cells (CTCs) in blood, known to be responsible for cancer metastasis, have been widely investigated as a biomarker for diagnosis and prognosis of metastatic cancer. In many of the studies, polymers have been commonly used to enable or enhance separation of CTCs; however, existing reviews do not focus on the role that has been played by polymers in the CTC detection field. In this review, we systematically classify the roles of polymers in representative CTC detection mechanisms, such as physical property-based filtration, separation in solution, and surface capture. This review highlights recent advances in the CTC detection through incorporation of polymers, which is a highly promising way to achieve clinically significant detection of rare CTCs.