Currently, data regarding optimal treatment modality, response, and outcome specifically for N3 head and neck cancer are limited. This study aimed to compare the treatment outcomes between definitive chemoradiotherapy (CCRT) to the neck and upfront neck dissection followed by adjuvant CCRT. Ninety-three N3 squamous cell carcinoma head and neck cancer patients were included. Primary tumor treatment was divided to definitive CCRT (CCRT group) or curative surgery followed by adjuvant CCRT (surgery group). Neck treatment was also classified into two treatment modalities: definitive CCRT to the neck (CCRT group) or curative neck dissection followed by adjuvant CCRT (neck dissection group). Overall, the 2-year overall survival (OS), local recurrence-free survival (LRFS), regional recurrence-free survival (RRFS), and distant metastasis-free survival (DMFS) were 51.8%, 47.3%, 45.6%, and 43.6%, respectively. In both oropharyngeal cancer and nonoropharyngeal cancer patients, in terms of OS, LRFS, RRFS or DMFS no difference was noted regarding primary tumor treatment (CCRT vs. surgery) or neck treatment (CCRT vs. neck dissection). In summary, N3 neck patients treated with definitive CCRT may achieve similar outcomes to those treated with upfront neck dissection followed by adjuvant CCRT. Caution should be made to avoid overtreatment for this group of patients.