Background: The objective of this study was to appraise the prognostic role of initial pan-endoscopic tumor length at diagnosis within or between operable esophageal squamous cell carcinoma (ESCC) undergoing upfront esophagectomy or neoadjuvant concurrent chemoradiotherapy (nCCRT) followed by esophagectomy. Methods: Between Jan 2001 and Dec 2013 in Koo-Foundation Sun Yat-sen Cancer Center in Taiwan, 101 ESCC patients who underwent upfront esophagectomy (surgery group) and 128 nCCRT followed by esophagectomy (nCCRT-surgery group) were retrospectively collected. Prognostic variables, including initial pan-endoscopic tumor length at diagnosis (sub-grouped <= 3, 3-5 and >5 cm), status of circumferential resection margin (CRM), and pathological T/N/M-status and cancer stage, were appraised within or between surgery and nCCRT-surgery groups. Results: Within surgery group, longer initial pan-endoscopic tumor length at diagnosis (= 3, 3-5 and >5 cm; HR = 1.000, 1.688 and 4.165; P=0.007) was an independent prognostic factor that correlated with advanced T/N/M-status, late cancer stage, and CRM invasion (all's P<0.001). Based on the initial panendoscopic tumor length at diagnosis = 3, 3-5 and >5 cm, nCCRT-surgery group had a poorer (P=0.039), similar (P=0.447) and better (P<0.001) survivals than did surgery group, respectively. For those with initial pan-endoscopic tumor length at diagnosis >5 cm, nCCRT-surgery group had more percentage of T0/N0status and stage 0 (all's P<0.05), and fewer rate of CRM invasion (P=0.036) than did surgery group. Conclusions: Initial pan-endoscopic tumor length at diagnosis could be a criterion to select proper ESCC cases for nCCRT followed by esophagectomy to improve survival and reduce CRM invasion.