Programmed death-1 ligand (PD-L1) expression has been used as a predictive marker for response to immune checkpoint inhibitors and has been reported to have prognostic value. Its prevalence and significance in endocervical adenocarcinoma (ECA) remain underinvestigated. We evaluated PD-L1 expression and CD8+ tumor-infiltrating lymphocyte density in whole tissue sections of 89 ECAs. PD-L1 expression was observed in 68% of ECAs by combined positive score (CPS, cutoff 1) and 29% of ECAs by tumor proportion score (TPS, cutoff 1%). Using CPS, PD-L1 expression was seen in 11%, 78%, and 72% of pattern A, B, and C tumors, respectively, with significantly higher expression in tumors with destructive-type invasion (B and C) (P=0.001 [A vs. B], 0.0006 [A vs. C], 0.0002 [A vs. B+C]). Using TPS, no significant difference in PD-L1 expression was seen between tumors with different invasion patterns (0%, 22%, and 32% in tumors with pattern A, B, and C, respectively; P=0.27 [A vs. B], 0.053 [A vs. C], 0.11 [A vs. B+C]). PD-L1-positive ECAs demonstrated significantly higher CD8+ tumor-infiltrating lymphocyte density (CPS: P=0.028; TPS: P=0.013) and worse progression-free survival when compared with PD-L1-negative ECAs (CPS: hazard ratio [HR]=4.253 vs. 0.235, P=0.025; TPS: HR=4.98 vs. 0.2; P=0.004). When invasion patterns were separately assessed, pattern C tumors similarly showed worse progression-free survival in PD-L1-positive tumors (CPS: HR=6.15 vs. 0.16, P=0.045; TPS: HR=3.78 vs. 0.26, P=0.027). In conclusion, our data show frequent PD-L1 expression in ECA with destructive-type invasion, supporting the role of the PD-1/PD-L1 pathway as a therapeutic target for these tumors. Our data also support PD-L1 as a negative prognostic marker associated with a potentially unfavorable outcome.