Background: According to several previous trials the rate of pathological complete response (pCR) for patients with TNBC is increased when carboplatin is added to NACT. However, it is largely unknown which group of patients would truly benefit from platinum-based NACT and for whom chemotherapy could be de-escalated. Several clinical trials have evaluated the stromal TILs as an important prognostic and predictive biomarker in breast cancer. We assessed the pCR rates and the outcomes in patients with TNBC randomized to receive NACT ± Carboplatin regarding TILs status. Methods: The clinical data were obtained from 132 patients diagnosed with TNBC (ER&PgR < 10%) and treated with either anthracycline-taxane NACT (n = 68) or сarboplatin-based chemotherapy (n = 64) from 2017 to 2022 at N.N. Petrov National Medicine Research Center of Oncology. TILs were evaluated in 132 formalin-fixed paraffin-embedded tumor tissue samples stained with H&E at baseline biopsies according to guidelines from the International TILs Working Group. Classification of TILs into low ( < 10%), intermediate (≤10% to < 40%) and high (≥ 40%) levels was performed. Data are presented using the methods of descriptive statistics. The differences between groups were assessed using the Сhi-square test. P-values below 0.05 were considered statistically significant. Results: The proportion of patients who achieved a pCR was higher in the carboplatin group 66% than in patients without carboplatin 35% (OR 3,5; 95% CI 1,71-7,17; p = 0,0006). There were 25 (18.9%), 77 (58.3%) and 30 (22.7%) patients with low ( < 10%), intermediate (≤10% to < 40%) and high (≥ 40%) levels of TILs, respectively. In total, the tumors with high TILs had a pCR rate of 63.3%, compared with 46.1% for low TILs (OR 2,0; 95% CI 0,87-4,67; p = 0,097). No significant statistical difference in pCR rates was shown between carboplatin-based and standard NACT groups with high TILs - 71% and 54%, respectively (OR 2,06; 95% CI 0,45-9,30; p = 0,346). When analyzing a group with low TILs infiltration, the pCR was more frequent in the platinum-based 64% compared to 31% in the standard NACT group (OR 3,9; 95% CI 1,72-9,00; p = 0,0011). Conclusions: These data may support the de-escalation of carboplatin-based NACT in patients diagnosed with TNBC with high TILs infiltration. Further investigations are warranted to explore the predictive value of TILs in platinum-based NACT.