To assess the clinical relevance and prognostic value of changes in the Naples prognostic score (NPS) after neoadjuvant chemoradiotherapy (NACR) among esophageal squamous cell carcinoma (ESCC) patients. We studied 232 locally advanced ESCC patients who received NACR before undergoing esophagectomy retrospectively. Categorizing individuals into the elevated NPS group and the non-elevated NPS group based on the change in NPS after NACR (ΔNPS > 0 or ∆NPS ≤ 0), we examined and compared the clinicopathological characteristics, survival rates, and postoperative complications between these 2 groups (∆NPS = post-NACR NPS - pre-NACR NPS). Results: Out of the 232 patients enrolled, 105 exhibited elevated NPS levels, while 127 showed non-elevated NPS levels. Survival analyses indicated inferior overall survival (OS) (p=0.024) and recurrence-free survival (RFS) (p=0.047) in the elevated NPS cohort compared to the non-elevated NPS cohort. Subsequent cox regression analyses identified the post-NACR change in NPS as an independent prognostic indicator for RFS (p=0.029) and OS (p=0.036). Elevated NPS post-NACR emerged as a significant indicator of worse prognosis for locally advanced ESCC patients who underwent NACR. This finding has great potential to be useful for recognizing high-risk ESCC patients who received NACR before undergoing esophagectomy and making individualized subsequent therapeutic decisions in clinical practice.