Radiotherapy is the mainstay and primary curative treatment modality in nasopharyngeal carcinoma (NPC), whose efficacy is limited by the development of intrinsic and acquired radioresistance. Thus, deciphering new molecular targets and pathways is essential for enhancing the radiosensitivity of NPC. SALL4 is a vital factor in the development and prognosis of various cancers, but its role in radioresistance remains elusive. This study aimed to explore the association of SALL4 expression with radioresistance of NPC. It was revealed that SALL4 expression was closely correlated with advanced T classification of NPC patients. Inhibition of SALL4 reduced proliferation and sensitized cells to radiation both in vitro and in vivo. Furthermore, SALL4 silencing increased radiation-induced DNA damage, apoptosis, and G2/M arrest in CNE2 and CNE2R cells. Moreover, knockdown of SALL4 impaired the expression of p-ATM, p-Chk2, p-p53, and anti-apoptosis protein Bcl-2, while pro-apoptosis protein was upregulated. These findings indicate that SALL4 could induce radioresistance via ATM/Chk2/p53 pathway and its downstream proteins related to apoptosis. Targeting SALL4 might be a promising approach for the development of novel radiosensitizing therapeutic agents for radioresistant NPC patients.