Background <p>Patterns of regional failure after intensity-modulated radiotherapy (IMRT) provide crucial evidence for optimizing target delineation in nasopharyngeal carcinoma (NPC). However, the specific patterns of regional recurrence after IMRT for NPC remain to be fully elucidated to optimize elective neck irradiation (ENI).</p> Methods <p>A total of 145 patients with NPC who developed regional recurrence after definitive IMRT between 2012 and 2022 were retrospectively reviewed. Recurrent lymph nodes were mapped onto the original pretreatment imaging, and each failure was categorized as either within or outside the initially involved field. Overall survival (OS) was estimated using the Kaplan-Meier method.</p> Results <p>Regional recurrence most frequently occurred in level IIb (55.1%), followed by level IIa (40.7%), level III (26.9%), level IV (17.2%), levels Va (11.7%) and Vb (11.0%), with infrequent involvement of the retropharyngeal (10.3%) and parotid (6.9%) regions. Most failures (95.2%) occurred within initially involved areas, while out-involved field recurrences were rare (4.8%), predominantly in the lower neck, and no skip metastasis was observed, suggesting a pattern of contiguous spread rather than de novo failure. The 5-year overall survival rate was 69.4%, and 74.2% among patients who underwent salvage surgery.</p> Conclusions <p>Regional recurrence after IMRT for NPC was mainly confined to initially involved areas, with out-involved-field recurrences being rare. These findings, combined with favorable outcomes following salvage treatment, serve as a valuable reference for optimizing ENI strategies.</p> Clinical trial number <p>Not applicable.</p>