Tumour infiltrating lymphocytes (TILs) are an established prognostic biomarker for triple-negative breast cancer (TNBC). We evaluated the role of programmed cell-death ligand-1 (PD-L1), CD8 and FOXP3 expression in refining a prognostic model for non-metastatic TNBC beyond classic factors and TILs. Primary tumour samples from 244 early patients with TNBC, all treated with surgery and chemotherapy, were collected. Stromal TILs were evaluated on haematoxylin–eosin slides according to guidelines. PD-L1, CD8 and FOXP3 were assessed by immunohistochemistry and evaluated by digital pathology. TILs, PD-L1, CD8 and FOXP3 were positively correlated with each other (P < 0.001). TILs were confirmed as an independent prognostic factor. When PD-L1, CD8 and FOXP3 were added to multivariable models including classic factors (age, stage, histologic grade) and TILs, PD-L1 provided the largest amount of additional prognostic information: likelihood ratio χ2 4.60, P = 0.032 (in a model including classic factors and TILs 10% increments) and likelihood ratio χ2 6.50, P = 0.011 (in a model including classic factors and TILs >30% versus <30%). In the subset of patients treated with neoadjuvant chemotherapy, FOXP3 provided further prognostic information beyond classic factors, TILs and pathological complete response (pCR) (likelihood ratio χ2 5.01, P = 0.025). For patients who did not achieve a pCR, the expression of CD8 and PD-L1 was significantly increased from baseline to residual disease. Beyond clinicopathological factors and TILs, other immune biomarkers may add prognostic information for early TNBC. The increased PD-L1 expression on residual disease after neoadjuvant chemotherapy strengthens the rationale of testing immune checkpoint inhibitors in the post-neoadjuvant setting. • Markers of immune activation are strongly prognostic in triple-negative breast cancer (TNBC). • Our results support the recommendation that tumour infiltrating lymphocytes (TILs) should be evaluated in TNBC. • Programmed cell-death ligand-1 (PD-L1) added significant prognostic information beyond classic factors and TILs. • PD-L1 expression is significantly increased on residual disease after neoadjuvant chemotherapy. [ABSTRACT FROM AUTHOR]