Papillary thyroid cancer (PTC) accounts for 80% of all thyroid cancers and seriously impacts the quality of people's lives. Long noncoding RNAs (lncRNAs) play an important role in PTC. In previous studies, thousands of lncRNAs were screened to study their potential relationships with PTC. The aim of this study was to investigate the effect of RPL34-AS1 in PTC and to explore its potential mechanisms. Bioinformatic analyses were performed to characterize the possible function and biological features of RPL34-AS1. Apoptosis, proliferation, and invasion were detected to assess the effect of RPL34-AS1. Cell proliferation was measured using a Cell Counting Kit-8 assay. Western blot analysis was used to assess the apoptosis proteins Bax and Bcl-2. Cell invasion was measured using a Transwell assay. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis was performed to examine RPL34-AS1, miR-3663-3P, and RGS4 expression. Dual-luciferase assay was performed to assess the binding of miR-3663-3P by RPL34-AS1. RIP experiment was used to verify the combination between miR-3663-3p and RGS4. We found that overexpression of RPL34-AS1 could inhibit proliferation and invasion while promoting apoptosis in PTC cell lines. Moreover, RPL34-AS1 could also competitively bind miR-3663-3p and exert its function by regulating the miR-3663-3p/RGS4 in PTC cell lines. We found a previously uncharacterized lncRNA, RPL34-AS1, and studied its function and mechanism in PTC. Our research will provide new insights into PTC and new clues for its clinical treatment.