Recent studies have confirmed the role of tumor-infiltrating lymphocytes (TILs) in carcinogenesis and cancer progression. The aim of this study was to evaluate the correlation between the level of tumor lymphocyte infiltration and well-known clinicopathological factors in breast cancer patients. We also evaluated the influence of TILs on overall survival. Paraffin sections were retrospectively evaluated in 76 cases in early stage breast cancer patients who underwent surgery followed by systemic treatment. Tumor-infiltrating lymphocytes were classified as absent (grade 0), mild (grade 1), moderate (grade 2), or severe (grade 3). Tumor-infiltrating lymphocytes were found in 87% of patients (severe grade in 8% of them). Higher grade (grades 2-3) TILs were present more frequently in younger patients (under 65 years) than older women (47% vs. 24%; p = 0.099). Higher grades of tumor-infiltrating lymphocytes (grades 2-3) appear to be associated with clinicopathological factors such as negative steroid receptor status (p = 0.001), HER2 overexpression (p = 0.016) and higher histological grade (G3) (p = 0.095). Tumor-infiltrating lymphocytes were not a significant prognostic factor for overall survival in our group. Only HER2 overexpression significantly increases the risk of death (HR = 4.3, p = 0.020). In the subgroup of patients who had tumors with HER2 overexpression there was non-significantly worse OS independently of TIL grade (p = 0.086).