Long non-coding RNAs (lncRNAs) possess both tumor suppressive and oncogenic functions in papillary thyroid cancer (PTC). Among all the thyroid cancers, PTC is the most prevalent form. Herein, we aim to determine the regulatory mechanisms and functions of lncRNA XIST in the multiplication, invasion, and survival of PTC. Quantitative reverse transcription polymerase chain reaction and Western blot experiments were performed to determine the patterns of lncRNA XIST, miR-330-3p, and PDE5A expressions. The subcellular localization of XIST was determined through subcellular fractionation. Bioinformatics analyses were performed to determine miR-330-3p's relationships with XIST and PDE5A, which were further confirmed through luciferase reporter assays. Loss-of-function combined with Transwell, CCK-8, and caspase-3 activity experiments were performed to determine the mechanism of the XIST/miR-330-3p/PDE5A axis in regulating the malignancy of PTC cells. Xenograft tumor experiment was employed to study the influence of XIST on tumor development <i>in vivo</i>. The PTC cell lines and tissues manifested considerably high levels of lncRNA XIST expression. The XIST knockdown inhibited proliferation, blocked migration, and strengthened apoptosis among PTC cells. Moreover, its knockdown suppressed PTC tumor development <i>in vivo</i>. XIST repressed miR-330-3p to stimulate the malignant behaviors of PTC. Through the downregulation of PDE5A, miR-330-3p attenuated the capability of PTC cells to grow, migrate, and survive. lncRNA XIST promotes tumor development in PTC through the regulation of the miR-330-3p/PDE5A axis. The findings from this study provide new insights into the treatment of PTC.