BACKGROUND Identification of simple and measurable prognostic factors is an important issue in treatment evaluation of breast cancer. The present study was conducted to evaluate the prognostic role of vascular invasion in lymph node negative breast cancer patients. METHODS in a retrospective design, we analyzed the recorded profiles of the 1,640 patients treated in the breast cancer department of Motahari clinic affiliated to Shiraz University of Medical Sciences, Shiraz, Iran, from January 1999 to December 2012. Overall and adjusted survivals were evaluated by the Cox proportional hazard model. All the hypotheses were considered two-sided and a p-value of 0.05 or less was considered as statistically significant. RESULTS Mean age in lymph node negative and positive patients was 50.0 and 49.8 respectively. In lymph node negative patients, the number of nodes, tumor size, lymphatic invasion, vascular invasion, progesterone receptor, and nuclear grade were significant predictors. In lymph node and lymphatic negative patients, vascular invasion also played a significant prognostic role in the survival which was not evident in lymph node negative patients with lymphatic invasion. CONCLUSIONS The results of our large cohort study, with long term follow up and using multivariate Cox proportional model and comparative design showed a significant prognostic role of vascular invasion in early breast cancer patients. Vascular invasion as an independent prognostic factor in lymph node negative invasive breast cancer.