Background: Breast cancer is a very common cancer that provides a significant amount of stress on patients’ lives. These patients can have many cancer-related complications, which lead them to present to the ED. However, few studies have identified common reasons for these patients to present to the ED and factors associated with high risk of admission. Methods: We utilized the 2006-2012 Nationwide Emergency Department Sample to identify the common primary diagnoses of breast cancer patients in the ED. A multivariate logistic regression was used to identify characteristics that were significantly associated with a higher chance of inpatient admission. A p-value less than 0.05 was considered significant. Results: Between 2006 and 2012, 2,160,701 breast cancer patients presented to the ED. Most patients were at least 80 years old (53.0%), female (99.1%), Medicare beneficiaries (64.4%), of the highest income quartile (26.2%), living in the South (36.8%), presented to non-trauma hospitals (52.7%), and presented to metropolitan non-teaching hospitals (44.8%). Most patients were admitted (53.1%). The most common primary diagnoses of breast cancer patients were chest pain (5.4%), urinary tract infection (3.3%), pneumonia (3.1%), secondary malignancy (3.0%), and cardiac arrhythmia (3.0%). The primary diagnoses associated with the highest risk of inpatient admission are the following: septicemia (odds ratio: 39.4, 95% confidence interval (CI): 33.8-45.9,p < 0.001), femur fracture (OR:19.1, 95% CI: 16.6-22.0,p < 0.001), secondary malignancy (OR:17.7, 95% CI: 16.2-19.4,p < 0.001), acute cerebrovascular disease (OR:5.8, 95% CI:5.3-6.3,p < 0.001), pneumonia (OR:4.9, 95% CI:4.7-5.2,p < 0.001), and complication of previous surgical or medical therapy (OR:2.2, 95% CI:2.0-2.3,p < 0.001). Primary diagnoses associated with a lower risk of admission are the following: contusion (OR:0.06, 95% CI:0.06-0.07,p < 0.001), abdominal pain (OR:0.14, 95% CI:0.13-0.15,p < 0.001), and connective tissue disorder (OR:0.17, 95% CI:0.16-0.19,p < 0.001). Interestingly, patients that paid with Medicaid (OR:0.84, 95% CI:0.79-0.89,p < 0.001) or private insurance (OR:0.89, 95% CI:0.86-0.93,p < 0.001) were less likely to be admitted. Furthermore, uninsured patients were also less likely to be admitted (OR:0.52, 95% CI:0.48-0.57, p < 0.001). Conclusions: Breast cancer patients frequently present to the ED for many reasons, with septicemia and femur being the most severe diagnoses. Physicians should keep these risk factors in mind to prevent these complications and reduce patient stress.