Circular (circ)RNAs have been implicated in cancer development. However, few studies have examined the role of circRNAs in papillary thyroid cancer (PTC). In this study we found that circNUP214 was upregulated in clinical PTC specimens relative to adjacent normal tissue. In vitro analyses showed that circNUP214 knockdown suppressed PTC cell proliferation, invasion, migration, and tumorigenesis. A luciferase reporter assay confirmed that circNUP214 binds to miR-145, which directly targets zinc finger E-box binding homeobox (ZEB)2. Thus, circNUP214 may play an oncogenic role in PTC by acting as a sponge for miR-145, leading to upregulation of ZEB2. These results provide evidence for a new regulatory mechanism in PTC development involving circNUP214, which can serve as a potential therapeutic target in PTC treatment. (C) 2018 Elsevier Inc. All rights reserved.