We investigated the efficacy and safety of 1-year atezolizumab treatment following 60 Gy of dCRT in patients with unresectable locally advanced ESCC....In 35 patients with an evaluable PD-L1 tumor proportion score, the cCR rates of <1% and ≥1% were 44.4% and 41.2%, respectively. Multiplexed immunohistochemistry of 38 evaluable patients indicated significantly higher tumor-infiltrating CD8+ T cells and PD-1+CD8+ T cells before dCRT in 15 patients with cCR than in 23 without cCR (p=0.0002 and 0.0020, respectively)....Atezolizumab monotherapy following dCRT resulted in a promising cCR rate and led to promising long-term survival. Tumor-infiltrating CD8+ T cells and PD-1+CD8+ T cells can serve as biomarkers for cCR.