Background: For primary TNBCs treated with NAC, higher pre-treatment TILs correlate with increased pathological complete response (pCR) rates, better recurrence-free survival (RFS) and overall survival (OS). We evaluated the prognostic value of RD TILs to pathological stage and Residual Cancer Burden (RCB) in predicting survival post NAC. Methods: We combined individual patient data from 4 TNBC patient series treated with NAC who did not achieve pCR. TILs were evaluated on the RD using our previously published method on H&E stained slides. TILs were investigated for associations with yp stage, RCB, RFS and OS using Cox models with stromal TILs as a continuous variable, stratified by series. The likelihood ratio (LR) test was used to evaluate added prognostic value of TILs to standard yp stage and RCB class. Results: In total 376 RD samples were evaluable for TILs. After 6 years median follow-up we observed 193 RFS events and 165 deaths. The median age was 50 years (range 24-83). 62% received combination anthracycline/taxane chemotherapy, and 27% anthracycline alone. For RD stage, 32% were yp node positive; RCB class I/II/III was 11%/50%/39% respectively. The median RD TIL level was 20% (IQR 10-40). TIL levels were significantly lower with increasing yp stage (P < 0.01), but did not differ significantly by RCB class (P = 0.84). Higher RD TILs were significantly associated with improved RFS (HR per 10% increment 0.86; 95%CI 0.79-0.92; P < 0.01) and OS (HR 0.87; 95%CI 0.80-0.94; P < 0.01), but were only significant for RFS in multivariate analysis after adjusting for yp stage (P = 0.03). RCB class was significant for RFS and OS (both P < 0.01). RD TILs added significant prognostic value to RCB class for both RFS and OS (both LR P < 0.01). The positive prognostic effect of RD TILs was of greater magnitude in the lower RCB classes I/II vs. III for both RFS and OS (both interaction P < 0.01). Conclusions: TIL levels in TNBC RD are significantly associated with improved RFS and OS and add further prognostic information to RCB class. The positive prognostic influence of TILs is significantly greater in patients with less RD burden. This data may help refine NAC clinical trial endpoints.