Introduction Young women under 30 years with breast cancer (BC) are an emerging challenge. The purpose is to identify prognostic factors for survival in young women under 30 years of age with BC. Material and methods A retrospective cohort study was conducted among women younger than or equal to 40 years with BC and who were treated at the State Cancer Center during the period 2012–2017. Overall survival was assessed using the Kaplan–Meier method and the log-rank test. Univariate and multivariate analysis assessed survival predictors using Cox proportional hazards regression model. Results 282 young women were included. The >30-year-old subgroup showed a significant association with excess weight ( P = .002) compared to the <30-year-old group. The <30-year-old subgroup showed a poor overall survival (56.7%), as well as highly significant values in advanced clinical stages, metastatic nodules, metastasis, and neoadjuvant therapy ( P < .001). In Model 3 of the multivariate analysis, age <30 years (HR = 3.0; 95% CI 1.1 to 8.6), triple negative subtype (HR = 2.6; 95% CI 1.1 to 6.0), tumor size >5 cm HR = 2.3; 95% CI 1.03 to 5.1), and advanced clinical stages (HR = 6.6 95% CI 1.3 to 35.5) persisted as predictors. Conclusions Being very young (<30 years) is a predictor for limited survival compared to the age of 30–40 years, as well as the tumor covariates for a worse prognosis: triple negative subtype, advanced stages, positive lymph nodes, and distant metastases in liver.