The present study investigated the clinical impact of neck lymph node (LN) metastasis in locally advanced inoperable thoracic esophageal squamous cell carcinoma (ESCC) patients who underwent concurrent chemoradiotherapy (CCRT) with a curative intent. There were 404 ESCC patients enrolled, including 35 patients with neck LN metastasis and 369 patients without such metastasis. Through the propensity score matching method, 35 patients of the 369 patients without neck LN metastasis were matched to the 35 patients with neck LN metastasis. Progression-free survival (PFS) and overall survival (OS) were found to be significantly worse in the neck LN metastasis group compared to the full non-neck LN metastasis group (9.8 months versus 5.9 months, P < 0.001, and 18.2 months versus 9.7 months, P = 0.001) and the matched non-neck LN metastasis group (9.9 months versus 5.9 months, P = 0.006, and 19.4 months versus 9.7 months, P = 0.007). In order to determine the difference between neck LN and supraclavicular LN metastasis, seventy patients with supraclavicular LN metastasis were also selected from the 369 patients without neck LN metastasis for comparison. Subsequently, when compared to the ESCC patients with supraclavicular LN metastasis, significantly worse PFS (8.5 months versus 5.9 months, P = 0.026) and OS (17.2 months versus 9.7 months, P = 0.047) were still found in the ESCC patients with neck LN metastasis. Our study indicates that neck LN metastasis is an independent poor prognostic factor for locally advanced inoperable thoracic ESCC patients who have undergone CCRT.