Objectives: . The mitochondrial ribosomal protein L14 (MRPL14) is encoded by a nuclear gene and participates in mitochondrial protein translation. In this study, we aimed to investigate the role of MRPL14 in thyroid cancer. Methods: . We investigated the association between MRPL14 expression and clinicopathological features using The Cancer Genome Atlas (TCGA) and Chungnam National University Hospital (CNUH) databases. Functional studies of MRPL14, including proliferation, migration, invasion, mitochondrial oxidative phosphorylation and reactive oxygen species (ROS) production, were performed in papillary thyroid cancer (PTC) cell lines (B-CPAP and KTC-1). Results: . Based on the TCGA dataset, PTC tissues lost mitochondrial integrity and showed dysregulated expression of overall mitoribosomal proteins (MRPs) compared with normal thyroid tissues. Of 78 MRPs, MRPL14 was highly expressed in thyroid cancer tissues. MRPL14 overexpression was significantly associated with advanced tumor stage, extrathyroidal extension, and lymph node metastasis. MRPL14 increased cell proliferation of thyroid cancer and promoted cell migration via epithelial-mesenchymal transition-related proteins. Moreover, MRPL14 knockdown reduced the expression of oxidative phosphorylation complex IV (MTCO1) and increased the accumulation of ROS. Cotreatment with a ROS scavenger restored cell proliferation and migration, which had been reduced by MRPL14 knockdown, implying that ROS functions as a key regulator of the oncogenic effects of MRPL14 in thyroid cancer cells. Conclusion . Our findings indicate that MRPL14 may promote cell growth, migration, and invasion by modulating ROS in thyroid cancer cells.