In the present study, to evaluate the role of Ku80 in thyroid carcinoma (TC), 86 thyroid tissue samples from patients with a spectrum of thyroid disorders were examined for protein levels of Ku80, nuclear factor‑κB (NF‑κB) and RET/TC by immunohistochemistry. Furthermore, in TC cells, Ku80 mRNA was detected by reverse transcription‑quantitative PCR analysis and silenced using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR‑associated protein 9 (Cas9) technique to assess its role. An antibody array was used to identify Ku80‑related regulatory genes. The protein levels of Ku80 in the TC tissues were significantly higher than those in non‑neoplastic adjacent tissue samples (P<0.01). The activation of NF‑kB and expression of RET/TC in the TC group were significantly increased (P<0.05) and were correlated with the protein expression of Ku80 (P<0.05). In papillary TC cells, the mRNA levels of Ku80 were high; Ku80 knockdown resulted in reductions in proliferation, invasion and colony formation, increased apoptosis, and reduced levels of proteins involved in MAPK signaling, cell proliferation and apoptosis. The high expression of Ku80 in TC was found to be associated with the expression of RET/TC and activation of NF‑κB, and Ku80 knockdown decreased the malignancy of TC cells.