Background: Breast cancer in young women is associated with aggressive biology. We analyzed histopathological and clinical properties of breast cancer patients diagnosed at ≤40 years of age. Methods: Breast cancer patients who were admitted between 2015 and 2019 were included. Baseline characteristics of the patients with treatment-related outcomes were assessed. The study group was divided into two subgroups; <35 years old as “very young” and ≥35 years old as “young.” Results: The data of 137 patients (60 patients <35 years) were reviewed. The mean age was 34.7 years. The mean follow-up duration was 44.45 ± 26.39 months, and the mean disease-free survival was 36.17 ± 21.97 months. 11.4% of the patients were diagnosed with Stage 4 disease. Pathologic subtype was invasive ductal carcinoma in 86% of patients. 16.8% of the patients were luminal A, 38.7% luminal B, 30.5% were human epidermal growth factor receptor-2–positive type, and 15.3% were triple-negative. Only 5 (3.3%) patients had given birth after chemotherapy. During the follow-up period of early-staged diagnosed patients, metastatic disease occurred in 24.6%. The rate of distant metastasis development was statistically higher in the very young group (31% vs. 11%; P = 0.004). Thirteen patients (10.7%) died due to disease progression. Thirty-seven percent of the patients had a positive family history for either breast or ovarian cancer. Conclusions: Very young breast cancer patients seem to have a more aggressive disease course. The low rate of childbearing in this young patient population is conspicuous. An interdisciplinary approach for the management of this special patient population should be taken into consideration.